Moria: The name used for the ancient dwarven mine of Khazad-dûm after TA 1980. It means 'The Black Chasm', but is sometimes translated as 'The Black Pit'.
Although in the Third Age the names Moria and Khazad-dûm seemed to be interchangable, the name Moria only truly applied to the mine after it was deserted by the Dwarves.
After the Dwarves left, the mine became dark and evil. There were orcs, trolls and one of the balrogs. The balrog was Durins Bane, who killed Durin and drove the dwarves out in the first place.
The Fellowship passed through Moria on their Quest for the Ring, and they all
came through to the other side except Gandalf the Grey who battled the balrog
and fell into the chasm.