(noun) the stage of an ancient Greek or Roman theater / (noun) the part of a modern stage in front of the curtain / (noun) the wall that separates the stage from the auditorium and provides the arch that frames it / (noun) foreground / (noun) foreground
it permits placing the racer's intimacy on the heroes' proscenium
The stage first broke through the proscenium arch, then outburst the brick-and-mortar integument of the theatre itself.