Farthen Dûr was a mountain in southeastern Alagaësia, in the center of the Beor Mountain range. Deep within Farthen Dûr lay the city of Tronjheim, the Dwarvish capital and long-time refuge of the Varden.
Much of Farthen Dûr's history remains a mystery. It was common knowledge that Dwarves are among the oldest races in Alagaësia and Farthen Dûr reflected that fact. In later years, however, the Dwarven race as a whole scattered into similar cities in other areas of the Beor Mountains and much of Farthen Dûr was abandoned. It was argued that the city should be abandoned, as it was a great drain on resources, but it served the valuable task of housing the entire dwarvish nation in times of great need, a task it performed on three occasions.
The Battle under Farthen Dûr was part of the Rider War which took place on the outskirts of Farthen Dûr. To win the battle, Eragon, the Varden and the Dwarves collapsed the tunnels that lead to the city and battled the Shade, Durza, as well as his army of Urgals, a conflict which ultimately resulted in the death of Durza and the shattering of the Isidar Mithrim.
Farthen Dûr housed both humans and Dwarves. The relationship between the two races was often strained, but it was effective. The Humans who resided in Farthen Dûr are generally members of the Varden. The Dwarves who lived there generally supported the Varden, but they did not directly contribute to the Varden's rebellious plans. Hrothgar, the king of the Dwarves, as well as Ajihad, the leader of the Varden, worked together to accomplish each other's goals, as did Orik and Nasuada, successors of Hrothgar and Ajihad, respectively.
"Farthen Dûr" means "Our Father" in the Dwarven language.