convertible stadium
A structure with raked seating around a performance area, and a movable roof which can be opened or fully closed.
Pictured: Minute Maid Park
A convertible stadium is a structure with raked seating around a stage or playing field, whose roof can be opened or fully closed, usually depending on the weather.
The movable roof allows the performance area to change between open and fully covered conditions. The raked seating remains part of the same stadium in either condition.
A fixed-roof indoor arena does not have this opening capability. An outdoor stadium has no full enclosing roof.