High Quality Content by WIKIPEDIA articles! A proscenium theatre is a theatre space whose primary feature is a large frame or arch (called the proscenium arch even though it is frequently not a rounded archway at all), which is located at or near the front of the stage. The use of the term "proscenium arch" is explained by the fact that in Latin, the stage is known as the "proscenium", meaning "in front of the scenery."