The Royal Shakespeare Company needed a temporary home for three years while it transformed and enlarged its permanent theater in Stratford-upon-Avon. The solution, devised by Ian Ritchie Architects, is a horseshoe-shaped 1,050-seat, thrust-stage auditorium situated within a windowless box. The box is built of folded Cor-Ten steel wall panels that were erected and bolted together as quickly as they will later be unbolted when the building is taken down. Cor-Ten is an oxidizing steel that creates its own deep-red, protective layer of "rust," and does not need painting. The self-effacing steel box, which has been likened to a "jumbo shipping container," unexpectedly harmonizes with its traditional surroundings. Without any of the trappings of iconic architecture, the Courtyard Theatre has been embraced by its public. The only problem is that it has become so popular, people may find it hard to leave.