The Door to Nothing
From SquackleWiki
The Door to Nothing is a portal inside of the Odin Shops bookstore that is literally a door to nothing. At first glance/door open, you see nothing but a wall, and wonder why there is a door there.
If the door is left open for exactly 3 minutes, it will suck you in and transport you into the Underbelly of Odin Shops.
