Bowser's Domain is The eighth world of Super Mario World U. The world features two different parts, an area above the ground and an area that is underground. There are 14 levels, 8 levels in part 1 and 6 levels in part 2. There are two fortresses, two castles, and does not feature any Mushroom Houses. Boom Boom is the boss for the first tower, Kamek is the boss for the second tower and the final castle is where Bowser is fought two times.