World 1 (New Super Mario Bros. Wii)
From the Super Mario Wiki
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World 1 (also known as Princess Peach’s Kingdom) is the first world in New Super Mario Bros. Wii. World 1 is occupied by Larry Koopa, the first boss to be fought in the game. This world features typical grassy plains with many colorful mushroom hills, similar to New Super Mario Bros. It has eight levels, three Toad Houses and a cannon. This world is also home of Peach's Castle. The enemy course features Goombas in three different sizes.