Goblin-gate
From Tolkien Gateway
The Goblin-gate, also known as Back-door[1] by the goblins, was a stone door serving as the lower eastern passage to the Goblin-town in the eastern side of the Misty Mountains.[2] It was located near the Eagles' Eyrie and west off the Carrock.[3]
The gate was built by the Orcs of the Misty Mountains "ages" ago both as a means of escape from their tunnels and as a way to access and harass the Wilderland. It was always guarded.[2]
Gandalf led Thorin and Company through that exit to escape the goblins. Bilbo Baggins also escaped from Gollum by squeezing through that stone door and losing his buttons.[4]