You can find the main entrance to the Dark Room in the Poptropica Towers area on Early Poptropica Island. It is located between a light green and light brown building. A fire hydrant and the Skateboard Kid are standing right beside it. There are two entrances to the Dark Room: one is on the ground of Poptropica Towers (which is in a form of a drain), and the other one is on the bottom left corner of the Pit. Once you enter the Dark Room, you will be in a maze. The ceiling and the ground are made of wood covered in vines, and the walls are made of dirt with words graffitied onto it.
It is a dark maze that can only be navigated by the glow stick found in the storage cavern. It can be accessed either by a manhole cover in Poptropica Towers, or by entering The Pit and travelling through the tunnel at the bottom left. You must get through the maze in order to get the Golden Egg to return to the Purple Giant. Along the walls are clues written to guide you along.