From the Super Mario Wiki
The Whoa Zone is an area in Chapter 4 of Super Paper Mario. It gets its name from its bizarre and somewhat disorienting appearance. According to Squirps, this area is also known as the "Space Graveyard," a prohibited zone and complicated maze. Squirps says it is impossible to get out of the area, and that the fifth Pure Heart is supposedly hidden at its end. Mario, Peach and Bowser must walk not only on the ground, but also on the walls and ceilings to traverse this area. Special blocks that either flip the player upside-down or rotate them clockwise appear to accomplish this. Some doors also change the location from the roof or walls. Many doors are in 3-D, and there are multiple paths to explore that hide keys. These paths are not hard to find or navigate, making the area seem less maze-like to the player. At the end of the maze waits Mr. L and Brobot, who are battled in space (although the background looks different than the usual space areas). After defeating Mr. L, the heroes discover that 1,500 years previously, Squirps had been instructed by Squirpina XIV to bring the heroes here so that they may claim the Pure Heart.
The Whoa Zone is reached by going through the Outer Limits. It is unknown if there is any other way to access the area. The Pure Heart in the maze may be the "legendary space treasure" the inhabitants of Planet Blobule were talking about.
The Whoa Zone appeared differently in the beta version of Super Paper Mario. It was briefly shown in Super Paper Mario's first trailer, where it was shown to have seemingly more circular elements in its background; the circles shown in this background were orange rather than the green color used in the final game. The Whoa Zone's greenish-brown doors were also normal, red doors in the beta game, and Mario was shown to wear his Space Helmet inside it during the trailer.
 Names in Other Languages