The Ered Gorgoroth or Mountains of Terror were a mountain chain in the north of Beleriand.
They were named such by the Sindar of Doriath after the spider-creature Ungoliant made it her temporary home, and spawned many evil spiders there, which wove webs that took away all light, and all the springs were poisoned.
South of the Gorgoroth lies the unpopulated land of Nan Dungortheb (the Valley of Dreadful Death).
The Gorgoroth had no known passes, and even the Orcs of Morgoth passed it by. In all of the First Age only Beren son of Barahir is said to have passed the mountain range, and he never spoke of this terrible journey.
Like the rest of Beleriand, the Gorgoroth were drowned during the War of Wrath, although the highland of Dorthonion survived as the isle of Tol Fuin.