Sequences in architecture: Sergei Ejzenštejn and Luigi Moretti, from images to spaces

The article ‘Montage and Architecture’ by Sergei Ejzenštejn, written between 1937 and 1940 and published posthumously, is one of the pivotal texts theorising montage as a method of composition, with a special focus on the potential of cinematic sequences in architecture. Despite the deep interest and the great number of studies that the publication of this text inspired in the last decades, Ejzenštejn’s analysis of the Basilica of Saint Peter, which occupies almost half of the article, has been overlooked. This article focuses on Ejzenštejn’s sequential interpretation of the Basilica and compares it with the one offered in 1952 by Luigi Moretti in the article ‘Strutture e Sequenze di Spazi’ [‘Structures and Sequences of Spaces’]. Examining Ejzenštejn’s and Moretti’s texts and related visual products, it develops a different way of considering the sequential qualities of the Basilica. Indeed, while Moretti proposes sequences as a method to design and represent three-dimensional spaces, the concept of montage as theorised by Ejzenštejn focuses on two-dimensional sequences as a tool to arrange images in space. The article proposes a series of possible common points between Ejzenštejn’s and Moretti’s theories, on the basis of a shared vision of sequences as mental constructs, and engages with a wider discussion on the dilemma between visual and spatial properties of architecture.


Introduction
Montage is a key theme of modern architecture and, despite several recent theoretical reinterpretations of the concept, its origins lie in the context of the twentieth-century avant-garde and in its relation with cinema. 1 Probably the most relevant text about montage and architecture is the essay by the Russian director Sergei Ejzenštejn, 'Montage and Architecture', published in English in the journal Assemblage in 1989. 2 As Davide Deriu has pointed out: Architectural historians have also paid increasing attention to montage at least since the 1980s, when its fundamental role in modernist avant-garde was ascertained. The English publication of a hitherto little-known essay by Sergei Ejzenštejn (written half a century earlier) contributed perhaps more than anything else to reposition this concept on the intellectual map of Anglophone architectural studies. 3 Before and after this publication of 'Montage and Architecture', Ejzenštejn's theories have attracted the attention of several architects and scholars, from Le Corbusier to Bernard Tschumi, and from Manfredo Tafuri to Anthony Vidler. 4 More recently, Martino Stiërli has put forward an interpretation of Ejzenštejn's theories in an entire chapter of his book Montage and the Metropolis: Architecture, Modernity and the Representation of Space (2018). According to Stiërli: The Soviet filmmaker and theoretician Sergei Ejzenštejn was certainly not alone among his avant-gardist colleagues when he assessed the potential of cinematic montage for rethinking the problem of representation. However, Ejzenštejn's contribution stands out, mainly for two reasons: first, unlike anyone else, he consistently worked toward a comprehensive theory of filmic montage throughout his entire career as a director […] Second, Ejzenštejn's take is of particular interest in our context because he frequently refers to architecture and urbanism as pre-cinematic media. 5 However, as Stiërli also points out, little interest has been given to Ejzenštejn's interpretation of the Basilica of Saint Peter in 'Montage and Architecture'. The majority of scholars avoid discussing this part of the Russian director's essay, regarding this case study as irrelevant in architectural terms. In his introduction to the article in Assemblage, Yve-Alan Bois underlines how the analysis of Saint Peter's is 'disappointing from an architectural point of view'. 6 Indeed, Ejzenštejn's analysis of the Basilica focuses more on sculpture than on architecture; the Russian director devotes 48% of his article (c. 3600 out of 7500 words) to the interpretation of the four plinths at the base of the columns composing the baldachin by Gianlorenzo Bernini, which is placed under the major dome, in the heart of the Basilica.
Yet, why does Ejzenštejn dedicate almost half of his essay to analysing a sculpture, instead of concentrating on the magnificent architectural qualities of the Basilica? What does this decision tell us about Ejzenštejn's interpretation of cinematic sequences and, more importantly, about his assessment of space in relation to montage? This article addresses these questions, using Luigi Moretti's sequential analysis of the Basilica of Saint Peter in his article 'Strutture e Sequenze di Spazi' ['Structures and Sequences of Spaces'] as a point of comparison to further investigate the role of sequences as a method to design and represent space, potentially overcoming the strict relationship with cinema and the visual realm. 7 Despite the numerous differences between the approaches of Moretti and Ejzenštejn, this article develops a systematic analysis of the two articles, focusing on the language and techniques of representation utilised by the two authors to describe sequences, and identifies some common points in their theories.

Sergei Ejzenštejn, 'Montage and Architecture'
The essay 'Montage and Architecture' was written by Ejzenštejn between 1937 and1940; it was published in English in 1989, with an introduction by Yve-Alain Bois. This text should be considered in relation to Ejzenštejn's primary aim to write a general theory of montage, in the late 1930s. 8 After theorising different kinds of montage (such as 'intellectual', 'metric', and 'rhythmic') in the 1920s, Ejzenštejn started looking at the possibility of defining the history of montage. He argued that montage is not a new invention of the avantgarde, but a compositive method that can be traced in all visual arts, today as in the past. 9 'Montage and Architecture' is divided into several parts, focusing especially on the role of composition in sequenceor montagewith reference to the field of architecture. After a brief introduction to the world of art, Ejzenštejn defines architecture as the ancestor par excellence of cinema, and explores several examples to support this thesis. In particular, he analyses the Acropolis of Athens starting from its famous description by Auguste Choisy; 10 he then examines some Catholic buildings including the Holy Mountains; lastly, he delves into the details of the sculptural elements of the baldachin of the Basilica of Saint Peter (1623-1634) in Rome by Gianlorenzo Bernini.
The system of comparison between cinema and other disciplines, which can be traced throughout the body of the theoretical work produced by Ejzenštejn, is aimed at highlighting the enormous potential of the concept of montage as a sequential process of elaboration through images that is applicable across the arts. 11 Over the years, the Russian director proposed various analyses and interpretative readings, reaching the point of defining montage as a truly interdisciplinary compositional method. Montage is not considered by Ejzenštejn as an automatic juxtaposition of a series of images, but as the 'law of the structure of the object'. 12 Montage is therefore an interdisciplinary, and also intellectual, instrument of construction that renders possible the organisation of a series of forms through a signifying scheme.
At the basis of the composition of its ensemble, at the basis of the harmony of its conglomerating masses, in the establishment of the melody of the future overflow of its forms, and in the execution of its rhythmic parts, giving harmony to the relief of its ensemble, lies that same 'dance' that is also at the basis of the creation of music, painting, and cinematic montage. 13 This interdisciplinary approach could lead to dangerous contaminations, as underlined by Bois. 14 But on several occasions, Ejzenštejn explicitly expressed his desire to demonstrate the procedural autonomy of editing in sequence, highlighting some of the main compositional characters beyond disciplinary boundaries, and especially without losing the essence of individual arts. 15 In 'Montage and Architecture' in particular, Ejzenštejn lays the foundations for a key comparison between architecture and cinema, starting from the concept of montage as a method of re-composing fragments, which has then been taken up by different designers and theorists. 16 He compares architectural composition to cinematic montage, underlining how both disciplines are related to the main aim of producing 'spatial constructions'. 17 ( Fig. 1). On the outer sides of the base of each of these four columns, Bernini created effigies of members of Pope Barberini's family. 18 The particularity of the work lies in the evident variation between the eight images: more specifically, the face of a woman placed at the top of the shield, is always represented with different expressions. This variation has led to the development of many interesting theories aimed at understanding the reasons behind it. The most accredited of them considers the different faces as illustrations of the stages of childbirth. Ejzenštejn himself seems to be especially interested in the various critical interpretations, as he refers to them in his article. 19 In any case, regardless of the real meaning or content hidden behind the sculpture, the compositional structure used by Bernini is fundamental for the Russian director. The presence of the eight different images induces a necessary movement around the baldachin: only in this way is it possible to understand the work in its entirety. As Ejzenštejn characteristically notes: The answer to the riddle lies entirely in that the full picture, the true 'image' of this montage statement only emerges in the sequential juxtaposition of its constituent 'frames'. Each shield, in itself means nothing. Viewed in isolation, it is dumb. […] In themselves, the pictures, the phases, the elements of the whole are innocent and indecipherable. The blow is struck only when the elements are juxtaposed into a sequential image. The placing of the shieldsor rather their 'displacing' around the four plinths, at right angles and at six meters distance from each other, together with the need to walk round the whole vast quadrilateral of the canopy and to begin from one particular corner (the left-hand front pillar) these are the factors that make up the cunning separation of the eight montage sequences. 20 The order in which the eight different faces are arranged is not random; a deliberate compositional sequence organises the succession of expressions to tell a story: the woman's face shows increasing suffering up to the last image of the newborn. There is therefore a precise order to follow, a pre-established movement that is necessary for understanding the work.
Despite the general lack of interest in this interpretation of the baldachin, 21 this study is actually key to further understand the spatial sequences proposed by Ejzenštejn for two main reasons. On the one hand, the composition, even if articulated in four-dimensional space, is somehow limited to the arrangement of a series of elementspictures, frames, imagesthat are simple surfaces; they do not have their own volumetric substance. Although Ejzenštejn tries to approach architecture in a specific way, within the discipline, his evaluation of space seems to remain tied to the two-dimensional frame of the camera. His 'cinematism' constrains architecture to serving as a locus of visual representation; it is explored in its three dimensions only because it offers a possibility of movement subordinated to the articulation of the choreographic path constructed by the images. 22 On the other hand, this striking example further clarifies Ejzenštejn's idea of montage applied in architecture. It shows that, despite the swirling baroque volume of the baldachin, what really drives the observer to walk around the baldachin is the meaning that underpins the experienceit is the narrative line that makes the movement necessary, in order for the visitor to recompose and understand the sequence of different shots. In this complex relationship between images, bodily movement, and meaningful experience, we recognise how Ejzenštejn's approach draws on the German aesthetic theories developed at the end of the twentieth century, and specifically that of August Schmarsow, as suggested by Martino Stiërli. 23 These theories proposed a novel idea of space that is not simply defined by geometry, but by the subject's psychophysiological elaborations, based on corporeal sensations and cognitive processes. 24 More specifically, Schmarsow considers 'visuality as key to a fully embodied experience of […] architectural structure', 25 while also stressing the more complex idea of an 'intuited form of space' consisting 'of the residues of sensory experience to which the muscular sensations of our body, the sensitivity of our skin, and the structure of our body all contribute'. 26 In several instances, Ejzenštejn expressed a similar interest in the psychophysiological reactions to montage, emphasising how the entire human body is part of the cinematic experience. Describing the Holy Mountains in 'Montage and Architecture', he wrote: The business of climbing that distance is particularly impressive because it is the custom to go from 'station' to 'station' and on up to the very topon one's knees. The emotional reaction from stopping place to stopping place thereby increases with the pilgrims' ever-increasing physical exhaustion. 27 Analysing the baldachin, Ejzenštejn carefully considered how the 'displacing' of the frames 'at right angles and at six meters distance from each other' can influence the spectator's pace and overall understanding of the sequence. Exactly like Schmarsow, Ejzenštejn recognises the significance of movement and bodily perceptions in processing the full emotional experience of cinematic forms in space, beyond the role of sight alone.

Luigi Moretti, 'Strutture e sequenze di spazi'
Luigi Moretti's 1952 article 'Structures and Sequences of Spaces' is another fundamental study of sequences in architecture. The aim of this text is to utilise the idea of sequential order to exalt the central role of empty space as a locus of experience in architecture. Following the critical line already firmly traced in Italy by Bruno Zevi at the time, 28 Moretti considered the void, or inner space, as the primary element of the project; he regarded it as a material to be shaped and defined through volumes and surfaces, and not as a simple result of their manipulation. To highlight the qualities and characteristic aspects of the hollow space inside buildings, Moretti uses various examples borrowed from the history of architecture, without distinguishing between epochs, styles, or typologies, and considers them according to the concept of sequences. In fact, what interests him is the experience obtained from the variations between spaces, to understand howby changing itselfthe void intervenes on the perception we have as we move through architecture.
And so, a study on the composition of these spaces and of the emotional course that their sequences suggest to us can perhaps bring to light certain points of the obscure law that universally guides the human spirit and drives great souls to compose such extraordinary architecture that moves even the minds of the simplest beholder. 29 As Moretti points out, his evaluations of 'experiential meaning' are linked specifically to the figurative terms of architecture. He is aware of the limits of these abstract considerations, which are disconnected from other variables of the project. But he defends their value in the critical analysis of the work, if this is followed by a contextualisation that can lead back to the overall vision. Moreover, according to Moretti, 30 the very theme of the internal hollow space is so central for architecture that even an analysis conducted solely on this parameter would be significant for evaluating the quality of the design. This is because many aspectsor 'spatial effects', 31 to use an expression of Emil Kaufmannrefer to, or reveal, singular features of the matter, while the void remains the negative of everything: a specular value capable of summarising all spatial effects by contrast and opposition.
I would like to limit this investigation to spatial unities formed by interior volumes that are composed in a certain order and that constitute, in their succession with changing perspectival effects and in relation to the courses and times necessary and possible for viewing them, a true sequence in the actual meaning of the term. Of these volumes, coordinated in unity, I intend to clarify the modalities of their succession and, therefore, the structure of their composition; that is, their type and the reasons for the concatenation of their volumes. 32 Moretti carries out a careful analysis of the modulations and variations of parameters in a series of case studies, highlighting the composition of spaces according to the logic imposed by various sequences. He defines four specific parametersor qualities specific to the empty spacethrough which to evaluate and compare the architectural works under examination: first, the geometrical shape, simple or complex; second, the size, or amount of absolute volume; third, the density, depending on the quantity and distribution of light that permeates the space; and fourth, the pressure or energetic charge, according to the proximity, more or less incumbent, of the constructive, confining masses, and of the ideal energies that they emit. The last one is a quality comparable to the pressure of a fluid in constant motion, subject to the obstacles and oppositions it encounters, or even to the potential of a space in relation to the electrical charges that affect it.

Luigi Moretti, the Basilica of Saint Peter
The case studies proposed in the article 'Structures and Sequences of Spaces' are analysed in detail starting from the parameters explained above: the sequences defined by Moretti are based on the composition of spaces in succession, which vary from each other according to one or more of these four terms. In the first instance, Moretti illustrates simpler sequences, where only one of the parameters is taken into consideration, such as the ternary group of Villa Adriana, where variations in the geometric shapes of the volumes create the succession, or the Palazzo Ducale in Urbino, in which the dimensions and proportions of the spaces vary. He then considers more complex and articulated sequences, where the succession is determined by the modulation of several parameters at a time, as in the churches of Guarino Guarini. 33 Moretti considers the sequence found in the Basilica of Saint Peter in Rome to be one of the most complex. In this case, Moretti focuses on the succession of rooms that lead from the entrance to the internal space under the majestic dome (Fig. 2). From the piazza, there is a first constriction element, the five access doors or pressure points, and immediately beyond them a first limited expansion in the atrium, accompanied by a vague sense of loss due to the longitudinal arrangement of the walls. This leads to a new barrier and pressure point, with a second series of forced entrances. After this second pause, we finally enter the immense and exceptional nave, with a crescendo of the volume dilated and widened into the dome.
Considering the spatial quality of the sequence, Moretti describes how, unlike the ternary group of Villa Adriana, in the Basilica of Saint Peter spaces in succession differ not only for their geometric shape, but also for variations of size and pressure, which create a complex sequence. Indeed, in the ternary group of Villa Adriana (composed by the portico of the Pecile, the square hall known as the Aula dei Filosofi, and the circular natatorium), the sequence is simply based on the variation of geometric shapes: prism, cube, and cylinder. In the case of Saint Peter's, in contrast, three parameters change and create the sequence. The first variation is the one of geometric shapes, in this order: transversal prism, longitudinal prism, sphere. The second one is a crescendo of sizes: from the 'great atrium' to the 'immense nave', until the 'empyrean of the cupola'. The last change is that of pressure: 'pressure (entry door), limited liberation (atrium), opposition (atrium walls), brief pressure (basilica doors), total liberation (transversal of the nave), and final contemplation (space of the central system)'. 34 The differentialsof geometry, size, and pressureinvolve an alternation of oppositions and reliefs that constitutes a rhythmic sequence, capable to form empty spaces with more varied characteristics: 'This pendularity has such a dominant and exclusive rhythm that it seems to reveal the movement, the very breath, necessary to the structure of the human spirit'. 35 Of equal interest is the consideration of the connecting points between the elements making up the sequence, which Moretti identifies in the narrow openings, or doors. These define the lyrical 'caesuras' that interrupt the rhythm and act as pivotal points to highlight the passage from one space to another. 36 We find these 'caesuras' between spaces, particularly in the case of the sequence in the Basilica of Saint Peter; they regulate the path of access and create a gradual process of abstraction, which leads to contemplation, to the empyrean empty space par excellence of the dome. Unlike Ejzenštejn's idea of a sequence of images, linked to the visual aspect of experience, here the elements placed in sequencethe spaces of the Basilicaare evaluated by Moretti according to their architectural qualities in a volumetric sense; they are no longer considered only as images or two-dimensional surfaces. However, despite these differences, both authors consider sequences as an instrument of composition capable of involving not only the human body, but also its emotional and cognitive perceptions. After all, Moretti also recognises the starting point of his theoretical assumptions in the works of German scholars of aesthetics, directly referring to Friedrich Ostendorf, Albert Erich Brinckmann, and August Schmarsow in his article. 37 Moreover, defending space as the core of architecture, the Italian architect is placing himself within a debate that had started in Germany but went far beyond, developed by Zevi and several other scholars of the interwar period, such as Sigfried Giedion, Nikolaus Pevsner, and Geoffrey Scott. 38

A comparison of sequential constructs
A thorough analysis of the language, means, and techniques utilised by Ejzenštejn and Moretti in their articles, allows us to further explore their positions through a systematic comparison. The goal here is to juxtapose the two authors' investigative methods, highlighting similarities and differences in their theoretical positions, to produce a wider discussion on sequences in architecture.
In Ejzenštejn's 'Montage and Architecture' there is an intense and reiterated use of the terms related to the visual realm, such as 'eye', 'view', and 'image'. The incipit of the article best exemplifies this: [When talking about cinema], the word path is not used by chance. Nowadays it is the imaginary path followed by the eye and the varying perceptions of an object that depend on how it appears to the eye. Nowadays it may also be the path followed by the mind across a multiplicity of phenomena, far apart in time and space, gathered in a certain sequence into a single meaningful concept; and these diverse impressions pass in front of an immobile spectator. In the past, however, the opposite was the case: the spectator moved between [a series of] carefully disposed phenomena that he absorbed sequentially with his visual sense. 39 Ejzenštejn here explains his intentions to compare cinema to architecture on the basis that both arts share the 'eye' as a device that allows the 'spectator' to sequentially understand the 'phenomena'. All these terms indicate a sequential experience mostly based on a visual perspective. Even the architectural sequence, defined in the last sentence, is perceived through the spectator's 'visual sense'. As suggested by Anthony Vidler, Ejzenštejn is comparing architecture and cinema through a 'spatial eye'. 40 On the other hand, an analysis of Moretti's article enables us to identify a very different use of terms. More specifically, in the first half of 'Structures and Sequences of Spaces', Moretti sets his analytical research parameters, defining his vocabulary and related contents. The article begins with the elements of architecture that inform his analysis: Architecture is understood through the different aspects of its form, that is, in the terms in which it is expressed: chiaroscuro, constructive fabric, plasticity, structure of internal spaces, density and quality of materials, geometric relationships of surfaces, and other terms more remote, such as colour, that from time to time may be asserted according to intangible laws of resonance. 41 From the outset, in Moretti's language we can indeed retrace his two cultural souls, as defined by Letizia Tedeschi, 42 one related to a strong humanistic passion, in particular for ancient and Baroque history, and the other tied to a scientific mind, that often characterises his theoretical approach. Therefore, in his article, we find terms such as 'structure', 'density', 'resonance', and also 'weight', 'energy', 'magnetic field', and 'potential distribution'. Borrowed from a techno-scientific vocabulary, these are used to develop a proper analytical research and support the rigour of Moretti's proposed theory. Terms such as 'chiaroscuro', 'plasticity', 'mass', 'quantity of volume', together with the selection of case studies, show Moretti's great passion for Baroque and sculptural spatial properties.
When we compare the two authors' linguistic choices for defining spatial sequences and their qualities, we trace an evident series of differences. The Russian director's selection of words is indeed closer to the visual, two-dimensional realm of the camera, while in Moretti's case words more properly describe the volumetric, architectural aspects of space. But when we further analyse the articles, focusing on the two authors' descriptions of their case studies in particular, we also identify some important shared aspects.
After the introduction, where he synthetically defines art's historical progression in relation to sequential properties, Ejzenštejn grapples with his two main examples: Auguste Choisy's interpretation of the Acropolis, and Gianlorenzo Bernini's baldachin. It is interesting to consider these case studies together to underline two common points. First, Ejzenštejn considers both cases from other scholars' perspectives; he never had the chance to visit either of them in person. 43 Considering this, we should not think that Ejzenštejn decided to focus on the baldachin 'instead of discussing the "maternal" space' of the church, as suggested by Bois. 44 We can argue that he discovered the studies about Bernini's sculpture and simply found them interesting. This is not a deliberate selection between two things: Ejzenštejn never had to physically cross the Basilica before seeing the baldachin. Second, Ejzenštejn looks at these oeuvres as films, and he literally asks the reader to do the same. 45 In this sense, he looks at the space of both examples through the synthetic, compressed vision of the camera lens.
However, another important difference between the analyses of the two case studies is their length. The first one occupies a little more than three pages, two of which are devoted to Choisy's text that Ejzenštejn quotes in full, while the second one is about seven pages long. 46 Ejzenštejn's examination of the baldachin is so long and dense, because he thoroughly investigates the meaning and the reasons behind the variation between the eight shields. If Ejzenštejn here is still using terms related to film, such as 'shoots' and 'montage', in this case he is also using other relevant words, such as 'drama', 'meaning', 'significance', 'story', 'allusions', 'satyr', 'sarcasm', and 'scope'. These words, and the length of the text they occur in, reveal Ejzenštejn's In a similar way, Moretti is not only interested in the 'composition of these spaces', but also in the 'emotional course that their sequences suggest to us'. 47 More specifically, if we consider the four parameters defined in 'Structures and Sequences of Space', there is one term that seems to be the most relevant and 'the most innovative quality because of its physical and emotional character', 48 and that is 'pressure'. In particular, describing the Basilica's sequence Moretti underlines how the parameter of pressure changes between the different spaces crossed, affecting the observer's emotions. Going beyond the morphological analysis, Moretti also explores the experiential meaning of the building, showing his humanist cultural approach to architecture that 'involves investigating, understanding, and representing human life', as suggested by his nephew Tommaso Magnifico. 49   Dupont. 50 Moretti himself considers sequences as narrative tools to be applied to different disciplines, in particular paintings and sculpture. When he writes about another famous sculpture by Bernini, he is also describing a sequence: Whoever circumnavigates the abstract world of the Fountain of Rivers, moving from one figurative island to the next, crossing seas and rhythmic spaces, sometimes narrow and sometimes deep, sometimes grandiose, sometimes crazily minute, is, afterwards, like a god who contemplates his living cosmos stilled in time and isolated in space. 51 For both authors, the meaning of sequences is ultimately determined by the subject's perception and experience. Ejzenštejn 'was indeed extremely concerned about the efficiency of films as forms to interact and involve people in the deepest and most perturbing ways'. 52 From his first theory of a 'Montage of Attractions' 53 to his latest works, we can read Ejzenštejn's attempt to maintain the expressivity and emotional features of films against some tendencies then promoted by other exponents of avant-garde cinema, such as Hans Richter and Dziga Vertov, among others. In a similar way, Moretti's interest in what moves the 'human spirit' is not conveyed only in his theoretical positions, 54 but also in some of his architectural works. These reveal an attraction 'for Expressionism and for focusing on the organic rather than the geometric', supporting 'an architecture of motion and emotion'. 55 Again, if we concentrate on the visual apparatus of the two articles, we will spot huge differences at first glance. For Ejzenštejn, drawing has always been a key tool. Some of the numerous drawings he produced during his career are more intimate, 56 while others are proper diagrams that enable him to compose his films, or become tools to analyse and study the works of others. 57 In 'Montage and Architecture', we find sketchesrather than proper drawingsthat belong to this third category. To represent the baldachin, Ejzenštejn utilises four main sketches. 58 Three of them can be read as a sequence of close-ups: starting from identifying the sculpture at the base of  the column as the main object of the investigation (Fig. 3), followed by the drawing of the relief on the same base (Fig. 4), and leading to the detail of the Pope's crown (Fig. 5). His last sketch is a diagrammatic plan used to show the distribution of views in space, whose sequential order is indicated by numbers from one to eight. In this sense, the plan seems to serve merely as an organisational scheme, while the elevationsor series of close-upsmore properly replicate the experience of the spectator. As argued by Steven Jacobs, Ejzenštejn 'elaborately discussed the inscription of time in a static picture and the sequential nature of aesthetic perception'. 59 Moretti also explored a broad variety of visual representation systems during his career. In 'Structures and Sequences of Spaces' he uses diagrams and models made by himself that clearly refer to the volumetric space and its complex perception. The models, in particular, are significant and fascinating illustrations of the buildings described, representing the interior of the architectural examples. They are physical concretisations of the void, three-dimensional negatives of the architectural space that clearly refer to the Zevian lesson, and in particular to the graphic tables accompanying the third chapter of Zevi's book Architecture as Space: How to Look at Architecture, first published in Italian in 1948. 60 The ensuing effect is surprising; Moretti's images are reminiscent of contemporary virtual models that highlight with extreme clarity the physical and material consistency of space, which seems anything but empty. In particular, the models of the Basilica of Saint Peter seem intent to explain the volumetric differentiations, from the most precisely detailed variation (Fig. 6) to the most complex whole sequence (Fig. 7). As argued by Viati Navone, Moretti's plaster models follow 'a graphic metalanguage, more useful for describing architectural spaces than the verbal language and canonical plans' already developed by 'August Schmarsow, Albert Eric Brinkmann, Paul Frankl, Hans Sedlmayr, but also by Vincenzo Fasolo, his professor at the school of architecture in Rome'. 61 Despite the two authors' different approaches in visually representing sequences, if we concentrate on Moretti's plan diagram of the Basilica of Saint Peter (Fig. 8), we find some similarities with Ejzenštejn's sketch plan of the baldachin (Fig. 9). Both are diagrammatic plans, abstracting the sequences, and proposing the elementary forms that induce to movement. In both drawings, the sequential order is underlined by figures (letters or numbers); the experience is perfectly synthesised as a balanced, carefully studied rhythm of variations.
Both authors are looking to their case studies for parameters, however different, that may vary (or not) from one element to another, finally creating the 'montage effect'. The physical and cognitive sequential experience is designed as a juxtaposition of elementsor 'collision of shots', and the figures used in their sequential drawings express a variation between these elements. Ejzenštejn wrote: The shot is a montage cell. Just as cells in their division form a phenomenon of another order, the organism or embryo, so, on the other side of the dialectical leap from the shot, there is montage. By what, then, is montage characterized  (private collection) and, consequently, its cell-the shot? By collision. By the conflict of two pieces in opposition to each other. 62 Compare Moretti: The qualities of realitythat is to say, the formarise from a complex of differences that are connected and follow one another in a certain ordera rhythm that constitutes the law of form itself. The group, in a mathematical sense generated by the differences, defines the form and therefore the quality. The group itself is not a quality but rather a complex of pure relationships between undifferentiated elementselementary signs. 63 Despite the differences in language discussed above, we can trace in the words of both Ejzenštejn and Moretti a common idea of 'form', or 'reality', which is defined through a variation between elements. This variation is the core of sequential constructs for both authors; without it, we cannot physically and cognitively elaborate the sequences that constitute spaces.

Conclusion
Sequences have been used in architecture since ancient times: the idea of composing a series of spaces following a specific order has often been considered an important feature of buildings. For Bernard Tschumi: Sequences of space, configurations-en-suite, enfilades, spaces aligned along a common axisall are specific architectural organizations, from Egyptian temples through the churches of the quattrocento to the present. All have emphasized a planned path with fixed halting points, a family of spatial points linked by continuous movement. 64 The tremendous impact that montage and Ejzenštejn's theories had on architecture, from the beginning of the twentieth century to the present, demonstrate the still vivid interest of architects in sequential constructs. The comparison pursued here between the two articles 'Montage and Architecture' and 'Structures and Sequences of Spaces' showed how sequences can be tied to images, especially if these are developed through the concept of montage. Yet, they can also be volumetric, eventually providing specific tools that enable architects to transgress the purely visual realm, and focus on the more complex design of space and its qualities. If Ejzenštejn considers the Acropolis a perfect example of 'ancient film', Moretti considers Greek architecture irrelevant for his discourse, as it is 'an algorithm of structures beaten by the sun'. 65 The Italian architect prefers to look at the masses and volumes of ancient Roman and Baroque architecture, because these can provide the most vivid sequential experience of space, in his opinion. On the other hand, the Russian director is interested in an architecture that can synthesise (without necessarily reducing) the whole complexity of physical experience to a series of images or perspectives. In this sense, one of the most famous quotes from Ejzenštejn's article, frequently mentioned by architectural scholars to highlight architecture's cinematic qualities, should be probably interpreted differently.
Painting has remained incapable of fixing the total representation of a phenomenon in its full visual multidimensionality.
[…] Only the film camera has solved the problem of doing this on a flat surface, but its undoubted ancestor in this capability isarchitecture. 66 If we read this carefully, we can understand that Ejzenštejn does not want to simply underline the 'capability' of architecture here: he is referring to the huge power of cinema in 'solving the problem' of representing 'a phenomenon in its full visual multidimensionality' on 'a flat surface'. In this sense, architecture is the old, ancient art that relies on real spaceand its physical limits while cinema is a brand new art that can properly represent the phenomena, synthesising spatial complexity through the screen. This is why the baldachin is an ideal case study: it tells a story in spaceso it is an architectural object in Ejzenštejn's viewcompressed into a series of frames.
Despite several evident differences, Moretti and Ejzenštejn would have probably agreed with Schmarsow that 'the experience of space is a combination of stored mental images and impressions perceived through ocular/bodily movement'. 67 It is exactly in this 'ocular/bodily' complexity that we can trace the issue of the dichotomy of 'an architecture as space versus an architecture as image' that 'may not have to be seen as so fundamentally antagonist altogether'. 68 In this sense, we must recognise that both authors contribute to the development of the same critical line on the assessment of space. Starting from German aesthetic theory and its vision of space as a mental construct through the later developments of the same concepts by Giedion and Zevi, 69 this assessment finally reconsiders the role of time in relation to space, thus creating the chance to revaluate the entire body and all its senses. Defining the concept of sequences according to this theoretical frame, Moretti and Ejzenštejn seem to share an interpretation of a sequential method of composition as the only design process that can actually transcend the physical space to finally create mental constructs, and modulate the emotive and intellectual perception of forms.