World 4 (Super Mario World 2: Yoshi's Island)
From the Super Mario Wiki
World 4 is the fourth world of the game Super Mario World 2: Yoshi's Island and Yoshi's Island: Super Mario Advance 3. It consists of 10 levels, and it has 6 regular Levels, a Fort, a Castle, an Extra Level, and the Match Cards Bonus Game. (Note: Its extra level is Extra 4: The Impossible? Maze; its secret level is Secret 4: Fight Toadies w/ Toadies.) The world's theme is an arid, mountainous area with sand, sand dunes, and scattered trees visible.
List of Levels