Theater

A place or building, consisting of a stage and seating, in which an audience gathers to watch plays, musical performances, public ceremonies, and so on.

A region where a particular action takes place; a specific field of action, usually with reference to war.

"His grandfather was in the Pacific theater during the war."

A lecture theatre.

An operating theatre or locale for human experimentation.

"This man is about to die, get him into theater at once!"