Diamond City

Diamond City is a location found in the WarioWare video game series. WarioWare: Twisted! confirmed that Diamond City is located on an island, though the exact location is unknown. It's a large city that's not only represented in the WarioWare series, but was also found as a stage in Mario Kart Arcade GP, which showcased more buildings such as a headquarters for Professor E. Gadd's company and plenty of shops. It's also been suggested that this is where Wario, among other characters in the game, lives.