Ered Luin:

The Ered Luin are the Blue Mountains. During the First Age, this mountain range was the eastern boundary of Beleriand. At the end of the First Age, they were split by the gulf of Lhûn. There were at least two dwarf-cities in the Blue Mountains during the First Age, and at least one partially survived as it is said that Dwarves still passed through the Shire on their way to their cities in the Blue Mountains.