World 1 is a world found in New Super Mario Bros. that serves as the first world as its name states where Mario and Luigi venture through. This world is revealed to be Mushroom Kingdom which features Princess Peach's Castle and is a grassland which grows grass and flowers. The mini-boss here is Bowser Jr. and the boss here is Bowser. This place also features 5 Mushroom Houses total and a Warp Cannon as well as a secret level.