Melkor's stronghold, built after he destroyed the two lamps it
was built under the Ered Engryn. Though it was partially destroyed
when the Valar captured Melkor, it was not completely cleaned out
and Balrogs and others still hid there during his captivity. After
he escaped from Valinor, Melkor rebuilt it and it was never again
taken until the Great Battle that ended the First Age of the Sun.
Angband was, of course, destroyed when the most part of Beleriand
sank beneath the ocean.