This is the place in your
high school where the
band was practicing. Usually there are halls outside the band hall which are lined with
practice rooms.
There is sometimes a room for percussion equipment, sometimes a room for
color guard stuff, and usually a place where the
uniforms are kept.
There is a giant rack along the back or one side of the band hall where the instruments are stored and a big
cabinet where the
sheet music is held in big folders. The
band director's offices are also connected to the band hall in one way or another.
The band hall proper should be a large
open space which would accomodate up to a few hundred
musicians. In smaller schools with small bands this will of course be a smaller space.