Prime examples of early Byzantine architecture date from the Emperor Justinian I's reign and survive in Ravenna and Istanbul, as well as in Sofia (the Church of St Sophia).

 One of the great breakthroughs in the history of Western architecture occurred when Justinian's architects invented a complex system providing for a smooth transition from a square plan of the church to a circular dome (or domes) by means of pendentives.

In Ravenna, the longitudinal basilica of Sant'Apollinare Nuovo, and the octagonal, centralized structure of the church of San Vitale, commissioned by Emperor Justinian but never seen by him, was built.
Justinian's monuments in Istanbul include the domed churches of Hagia Sophia and Hagia Irene, but there is also an earlier, smaller church of Saints Sergius and Bacchus (locally referred to as "Little Hagia Sophia"), which might have served as a model for both in that it combined the elements of a longitudinal basilica with those of a centralized building.

Other structures include the ruins of the Great Palace of Constantinople, the innovative walls of Constantinople (with 192 towers) and Basilica Cistern (with hundreds of recycled classical columns).
A frieze in the Ostrogothic palace in Ravenna depicts an early Byzantine palace.

Hagios Demetrios in Thessaloniki, Saint Catherine's Monastery on Mount Sinai, Jvari Monastery in present-day Georgia, and three Armenian churches of Echmiadzin all date primarily from the 7th century and provide a glimpse on architectural developments in the Byzantine provinces following the age of Justinian.

Remarkable engineering feats include the 430 m long Sangarius Bridge and the pointed arch of Karamagara Bridge.

The period of the Macedonian dynasty, traditionally considered the epitome of Byzantine art, has not left a lasting legacy in architecture.
It is presumed that Basil I's votive church of the Theotokos of the Pharos and the Nea Ekklesia (both no longer existent) served as a model for most cross-in-square sanctuaries of the period, including the Cattolica di Stilo in southern Italy (9th century), the monastery church of Hosios Lukas in Greece (c. 1000), Nea Moni of Chios (a pet project of Constantine IX), and the Daphni Monastery near Athens (c. 1050).

The Hagia Sophia church in Ochrid (present-day North Macedonia),  Iole in times of Boris I of Bulgaria, and the eponymous cathedral in Kiev (present-day Ukraine) testify to a vogue for multiple subsidiary domes set on drums, which would gain in height and narrowness with the progress of time.
Prime examples of early Byzantine architecture date from the Emperor Justinian I's reign and survive in Ravenna and Istanbul, as well as in Sofia (the Church of St Sophia). 
 One of the great breakthroughs in the history of Western architecture occurred when Justinian's architects invented a complex system providing for a smooth transition from a square plan of the church to a circular dome (or domes) by means of pendentives.
In Ravenna, the longitudinal basilica of Sant'Apollinare Nuovo, and the octagonal, centralized structure of the church of San Vitale, commissioned by Emperor Justinian but never seen by him, was built. Justinian's monuments in Istanbul include the domed churches of Hagia Sophia and Hagia Irene, but there is also an earlier, smaller church of Saints Sergius and Bacchus (locally referred to as "Little Hagia Sophia"), which might have served as a model for both in that it combined the elements of a longitudinal basilica with those of a centralized building.
Other structures include the ruins of the Great Palace of Constantinople, the innovative walls of Constantinople (with 192 towers) and Basilica Cistern (with hundreds of recycled classical columns). A frieze in the Ostrogothic palace in Ravenna depicts an early Byzantine palace.
Hagios Demetrios in Thessaloniki, Saint Catherine's Monastery on Mount Sinai, Jvari Monastery in present-day Georgia, and three Armenian churches of Echmiadzin all date primarily from the 7th century and provide a glimpse on architectural developments in the Byzantine provinces following the age of Justinian.
Remarkable engineering feats include the 430 m long Sangarius Bridge and the pointed arch of Karamagara Bridge.
The period of the Macedonian dynasty, traditionally considered the epitome of Byzantine art, has not left a lasting legacy in architecture. It is presumed that Basil I's votive church of the Theotokos of the Pharos and the Nea Ekklesia (both no longer existent) served as a model for most cross-in-square sanctuaries of the period, including the Cattolica di Stilo in southern Italy (9th century), the monastery church of Hosios Lukas in Greece (c. 1000), Nea Moni of Chios (a pet project of Constantine IX), and the Daphni Monastery near Athens (c. 1050).
The Hagia Sophia church in Ochrid (present-day North Macedonia),  Iole in times of Boris I of Bulgaria, and the eponymous cathedral in Kiev (present-day Ukraine) testify to a vogue for multiple subsidiary domes set on drums, which would gain in height and narrowness with the progress of time.
Byzantine architecture