Moria is the underground city where the Fellowship encounters a Balrog in J.R.R. Tolkien’s The Lord of the Rings.
Moria was originally called Khazad-dûm by the Dwarves. It was a vast kingdom and mining complex beneath the Misty Mountains, famous for its wealth of mithril. After the Dwarves awakened a Balrog, they abandoned the city, and it became known as Moria, a name associated with darkness and danger.
The Fellowship enters Moria while traveling south after leaving Rivendell. Inside, they discover evidence of the Dwarves’ destruction, including the chamber of Balin’s tomb. Their escape leads to the Bridge of Khazad-dûm, where Gandalf confronts the Balrog and falls into the abyss.
Khazad-dûm and Moria are names for the same place, which is why they can seem like separate answers. Gondolin is another underground or hidden Elven city, but it belongs mainly to the First Age and is not the Fellowship’s destination.