Annon-in-Gelydh
From Tolkien Gateway
Annon-in-Gelydh (S. "Gate of the Noldor]]") was the eastern entrance in the western hills of Dor-lomin, that led to a subterranean river-bed and ended to the Cirith Ninniach.
It was built by the Noldor of Turgon in the First Age. After Turgon's departure to Gondolin, the Gate was forgotten, but it was rediscovered and used centuries later by Tuor in his escape from the oppressed lands of Hithlum and find his way into Nevrast.[1]