Khazad-dûm:

The home of Durin, the eldest of the Seven Fathers of the Dwarves, Khazad-dûm was the greatest of the Dwarven mansions, especially after the destruction of Beleriand which partially destroyed Nogrod and Belegost. Many dwarves fled from Nogrod and Belegost to Khazad-dûm, swelling its population. Khazad-dûm was the only place where mithril could be found, but mithril was also the cause of their destruction, as in mining for mithril, they accidentally freed the Balrog. The Dwarves abandoned Khazad-dûm in the year 1981 of the Third Age. After the Dwarves left, Sauron sent orcs to gather all the mithril, gold and jewels that could be found. The Elves called Khazad-dûm Moria, the Black Chasm afterwards. It was in Moria that Gandalf fell fighting the Balrog.

There was a prophecy that one day the Dwarves would retake Moria, referred to in the following:

And the line of Dain prospered, and the wealth and renown of the kingship was renewed, until there arose again for the last time an heir of that House that bore the name of Durin, and he returned to Moria; and there was light again in deep places, and the ringing of hammers and the harping of harps, until the world grew old and the Dwarves failed and the days of Durin's race were ended.(HOME XII.278)
So ended the attempt to retake Moria! It was valiant but foolish. The time is not come yet. (LOTR.341)

The Hobbit
The Lord of the Rings
The Silmarillion
The Peoples of Middle-Earth (HoME XII)
The Complete Guide to Middle-Earth by Robert Foster
The Unfinished Tales