World 2 (New Super Mario Bros. Wii)
From the Super Mario Wiki
World 2 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 Starmans, Mushrooms, and Propeller Mushrooms. On the map, there is an area where Mario and the gang can get sucked into the sand and play in a level where they have to collect all the Toad Balloons without dying.