Har Kaldra

Known now as the Forgotten City, Har Kaldra was once a mighty fortress that dominated the landward passes between Naggarond and the Ironfrost Glacier. Now it is a scarred and ruined crater, surrounded by the outflung remnants of its own walls, a testament to Malekith's fickle rage. It was the Witch King that wrought Har Kaldra's ruin, meeting the rebellion within its walls with all the sorcerous might at his command. Thousands perished in that one night of horror and fury, and thousands more were taken in bondage to Naggarond, there to die in its firepits and gladiatorial arenas.

Source

 * Warhammer Armies: Dark Elves (8th Edition) -- p. 13.