World 2 (New Super Mario Bros. Wii)
From the Super Mario Wiki
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World 2 (also known as the Desert World) is the second world in New Super Mario Bros. Wii. The levels are all desert themed. There are eight levels in this world, two of them being castle levels that are guarded by Roy Koopa. Various Mushroom Houses are also found around here, giving the player items such as Stars, Mushrooms, and Propeller Mushrooms. On the far area of the map, holes appear in the sand to try to drop Mario and the gang in, making them play in the Enemy Course, a level where they have to collect all the Toad Balloons without dying.