Mines of MoriaMoria - Originally the home of the Dwarves under the Misty Mountains.  Later they were driven out by a Balrog.  Finally, the great halls were occupied by Orcs.

 

"He raised his staff, and for a brief instant there was blaze like a flash of lightning.  Great shadows sprang up and fled, and for a second they saw a vast roof far above their heads upheld by many mighty pillars hewn of stone.  Before them and on either side stretched a huge empty halls; its black walls, polished and smooth as glass, flashed and glittered.  Three other entrances they saw, dark black arches: one straight before them eastwards, and one on either side.  Then the light went out." ~The Fellowship of the Ring, Book II, chap. 4 (A Journey in the Dark)