great hall

noun2

1. •
   The main room of a palace, castle or large manor house in the Middle Ages, or in a country house of the 16th and early 17th centuries.

   • Even in castles and manor houses space was limited, and rooms including the great hall were used for other functions beyond dining. — 2004
2. •
   The principal building of a manor or castle compound.

   • "Now this" — he indicated the great building facing them, with a handsome flight of steps up to the open door — "this is the great hall." — 2005