World 6 (Yoshi's Woolly World)
From the Super Mario Wiki
World 6 is the sixth world of Yoshi's Woolly World. It is a mostly volcanic-themed world, featuring elements related to lava and ashy clouds. As in all other worlds, there are nine levels: eight compulsory, and one special level that is unlocked after all other Smiley Flowers in the previous levels in the world are collected. The main levels are located in drawers and the castle is on top.