The unsung heroes of theatre The Cardiff exhibition also demonstrates how eclectic and resourceful stage designers are: the variety of styles and approaches across over 100 stands is breathtaking. The Americans don't seem to produce much interesting work, nor is there sign of much originality coming out of France, Germany or Italy: the fresh thinking and wilder experiments seem to stem more from Scandinavia, Eastern Europe, South America and Eastern Asia. But it isn't all outré concepts: the best stage designers aren't the dreamers so much as the practical craftsmen and problem-solvers who can make magic out of the most unpromising materials, be it papier-mâché or corrugated iron. Many of the British representatives are relatively mainstream, but none the less impressive for that: they include Es Devlin, who designed the Union Jack floor for the Olympic closing ceremony (and whose name should have been honoured alongside director Kim Gavin's); Hildegard Bechtler, Jean-Marc Puissant, Isabella Bywater, Johan Engels and Leslie Travers, who contribute richly textured and evocative designs for opera; and Tom Piper and Michael Pavelka, who do the same for Shakespeare. But the territory of stage design is no longer demarcated by models of sets and sketches for costumes destined for indoor, artificially lit theatres: the domain has been vastly extended by the vogue for site-specific installation and immersive journeys, and the genres of video, light art, sound art and land art. As we see at the RWSMD exhibition, the designer also has to lead the audience on a journey, clear a space for chaos or transform a public space - Simon Banham designs Coriolanus in an aircraft hangar, Louise Ann Wilson designs a performance which takes place over three days walking in the Yorkshire Dales. Browsing through this fascinating exhibition, which starts in the main foyer of the RWCMD, could absorb you happily for an hour or two. But do save a little time to look at a related project in the Anthony Hopkins courtyard - here stands the winner of the sustainable theatre competition, which solicited designs for a temporary structure for performance, entirely recyclable and assembled within ten days for a meagre budget of £20,000. Over a hundred entries were submitted for this challenge: what came out top is Brad Steinmetz and Tim Lai's Willow Theatre, constructed on a simple scaffolding frame sheeted and roofed in polythene, its exterior hung with pennants of white gardener's fleece which flutter alluringly in the wind. Inside is nothing but bleacher seating for 100, a platform and a simple lighting rig - it's a simple and beautiful thing, proof against cuts and recession, and reminding us that you don't needs expensive fittings - or even bricks and mortar - to lay the foundations of living theatre. World Stage Design 2013 runs at Royal Welsh College of Music and Drama, Cathays Park, Cardiff (029 2039 1391) until September 14; wsd2013.com