The main stage is with a proscenium arch. The audience is usually separated from the performers by the proscenium arch. A stage with a proscenium arch was located on the west end. The grand foyer columns and auditorium proscenium arch were more recent restorations. It is usually a heavy fibreglass or iron curtain located immediately behind the proscenium arch. The proscenium arch housed a drop curtain. The central stage proscenium arch employed the most modern technology of the time. Bert walks upside down on the proscenium arch over the stage. In dance history, the use of the proscenium arch has affected dance in different ways. The high proscenium arch is decorated with a circular medallion flanked by gryphons. The proscenium arch was outlined with climb-ready scaffolding. The wide proscenium arch is the widest in Europe. When a proscenium arch has been used, its usual use has often been subverted. A proscenium arch creates a "window" around the scenery and performers. The proscenium arch evolved from the "proskenium" in Ancient Greek theaters.