Flipside
Flipside is a mysterious interdimensional town in Super Paper Mario, created by the Ancients. Flipside is odd and irregular toward most things in the Marioverse, introducing a whole new style of area. Flipside has different "floors" which can be acessed by mysterious elevators interconnected with each other. Paths to many worlds can be opened from there. Flipside Tower, located in the middle of the town, controls the flow of dimensional energy to teleport people to other worlds. There is a mirrored version of Flipside called Flopside.
The sky of Flipside is strange and whitish-yellow with many geometric cubes and symbols hovering around. The people of Flipside are peculiarly pixel-like and have bodies made of separate layers.
It was built by the Ancients.
There is also an area outside of the town of Flipside called Flipside Outskirts. It seems to be a strange, interdimensional wasteland with monsters on its paths.
Almost every structure in Flipside, despite a few places and roofs, is whitish or gray with a hint of yellow.