ancient theatrical device by which a scene or change of scene was indicated. It was described by Vitruvius in his De architectura (c. 14 BC) as a revolving triangular prism made of wood, bearing on each of its three sides a different pictured scene. While one scene was presented to the audience, the other two could be changed. Although it was once thought to be a feature of Greek classical drama, it is now believed that it did not originate until the Hellenistic age. The periaktos was revived, notably for the Italian theatre in about 1500 and for the 17th-century English stage.