- The opening that separates the stage from the audience. Itnormally has a curtain (and the safety curtain demanded by fire regulations).One of the first proscenium arches was built for the Teatro Farnese,which opened in 1628 in Parma, Italy. Early English examples had aprons,or forestages, for acting in front of the proscenium arch; these beganto disappear in the early 19th century, reinforcing the sense of theaction taking place within a picture frame. The opening can be reducedin size by using flats or cloths to create a false proscenium(known in America as a portal opening). Many modern directorsregard the proscenium arch as a barrier to interaction between actorsand audience, and for this reason modern theater designs often usean open stage plan or arena setting (see theater-in-the-round).