Belegost was one of two great underground Dwarven cities in the Blue Mountains, the other being Nogrod, that prospered during the First Age. It was home to the Dwarves of Belegost.
Geography
Belegost was delved in the eastern side of the north-central part and of the Blue Mountains northeast of Mount Dolmed where the Dwarf-road of Beleriand crossed into Eriador, guarding one of the only passes over the Blue Mountains not far from lake Nenuial.
Belegost was founded during the Years of the Trees when the western Fathers of the Dwarves awoke from beneath the Blue Mountains.
In Y.T. 1250 the Dwarves of both Nogrod and Belegost became known to the Sindar, and though friendship between the Elves and Dwarves was cool, they had much profit of each other and Thingol welcomed them.
Around Y.T. 1300, the Dwarves of Belegost were called upon by Thingol to aid in the building of Menegroth. The Dwarves laboured long on this, though they were eager for new works and did so gladly; they ever demanded a price for their work, but considered themselves paid between receiving the wisdom of Melian and many fair pearls, including Nimphelos, from Thingol.
During the late First Age, Azaghâl was the Lord of Belegost until he was killed in the Nirnaeth Arnoediad.
At the end of the First Age, Belegost was ruined in the War of Wrath. Around the S.A. 40 many Dwarves migrated from Belegost to Khazad-dûm. and brought much lore and craft with them. However, some Dwarves remained on the eastern side of the Blue Mountains.