Greg's (Dream) Bunker

Greg's (Dream) Bunker was an imaginary bunker Greg designed for himself in the future in Book.14, Wrecking Ball.

Basic Description
Greg designed it to look like a normal house on the outside but to be a 5-storey bunker underneath. Features include a bathtub in a giant aquarium, an arcade room, a bowling alley, and other things. He later uses it for ideas for an extension.