Thangolos is an ancient primeval forest of Elrohir Mithrandír. It is dense, dark place. The trees of Thangolos are colossal in size. Many rocky hills and numerous ravines make travel difficult. Many streams, pools and lakes are about the forest, some of them cover half-submerged ruins of the lost civilization that once reigned here. Thangolos is between two mountain ranges, Bullvar Ika and Syrmal. As a result there are numerous streams, ponds, and lakes in that area. Some of these fall into chasms and then plunge through sinkholes into the Underdark. Thangolos ends in the south at the wastelands of the Magnothor volcano.