In the J. R. R. Tolkien fictional universe of Middle-earth, Mirrormere is the lake located beneath the doors of Khazad-dûm. It is known as Kheled-zâram by the Dwarves.
According to the Dwarves of Durin's folk, after Durin the Deathless had awoken at Mount Gundabad in the north of the Hithaeglir (Misty Mountains), he travelled south until he came upon this lake. He looked down in it, and saw a crown above his head. This crown was the reflection of stars above, despite the fact it was day and the stars should not have been visible. Then he founded Khazad-dûm at that place.
During the events that led up to the War of the Ring, the Fellowship of the Ring passed by the lake after escaping Moria. Despite their hurry, Gimli would not pass by without looking in the lake. Frodo Baggins joined him, and both saw Durin's crown.
