Mount DoomMt. Doom - The mountain where the Ring of Power was forged, where the last great battle of the Second Age was fought and where the One Ring was finally destroyed.  Called Orodruin in Sindarin.

 

"Sam was looking at Orodruin, the Mountain of Fire.  Ever and anon the furnaces far below its ashen cone would grow hot and with a great surging and throbbing pour forth rivers of molten rock from chasms in its sides.  Some would flow blazing towards Barad-dûr down great channels; some would wind their way into the stony plain, until they cooled and lay like twisted dragon-shapes vomited from the tormented earth.  In such an hour of labour Sam beheld Mount Doom, and the light of it, cut off by the high screen of the Ephel Dúath from those who climbed up the path from the West, now glared against the stark rock faces, so that they seemed to be drenched with blood." ~The Return of the King, Book VI, chap. 1 (The Tower of Cirith Ungol)