From the Super Mario Wiki
Wario Park is the amusement park that Wario built in WarioWare: Snapped!. It serves as the main setting for the game, and its main attractions are its four roller coasters. Mona, Jimmy T., and Kat and Ana volunteer to work at the park, and each runs their own roller coaster. The roller coasters have loops and appear to be essentially the same, only differing in their color and design.
According to Wario, Wario Park is "the world's wackiest theme park", although not much is known about it. It is unknown how Wario built it, but as usual, his motivation was to earn money. As seen in the picture, it appears that there are several other attractions located in the park aside from the roller coasters, but the player cannot visit them.
Wario and his friends all have different costumes for the park.