Entrance to Crows Nest

The Crow's Nest Entrance is an Easter Egg on the Campaign level Sierra 117. It is an area that is shown in a cutscene at the end of the level.

Tutorial
To get there, you need to first get out of the map using a glitch. After you're out, you need to walk past the Lone Caveman, and go up the path to your left. CAUTION: DO NOT HAVE EVERYBODY IN THE GAME GO DOWN INTO THE PIT BECAUSE THERE IS NO WAY OUT! That being said, have one player stay out of the pit, and one go in, and when they're done exploring, have them commit suicide.