Dimrill Dale (Nanduhirion in Sindarin and Azanulbizar in Khuzdul) was a valley on the east side of Misty Mountains, beneath the Redhorn, Silvertine, and Cloudyhead peaks. It was the eastern end of Redhorn Pass and was bordered by the Dimrill Stair. Dimrill Dale was the source of the Silverlode river. At its southeast corner was Mirrormere, a sacred lake to the Dwarves of Durin's folk.
During the Years of the Trees, Durin the Deathless wondered south to Dimrill Dale and founded the Kingdom of Khazad-dûm beneath the surrounding mountains. Thousands of years later, after Orcs had turned the Dwarven city into the "Black Pit" of Moria, the deciding battle of the War of the Dwarves and Orcs was fought here. The Battle of Azanulbizar which occurred in the Third Age 2799, ended as a defeat of the Orcs and their leader Azog. The Dwarves, though, were unable to take back Moria because of the Balrog that still dwelled there.
The name Dimrill means "overshadowed rills" referring to the rills that ran down the mountain-side.