World 4 (Super Mario 3D Land)
From the Super Mario Wiki
Ads keep the MarioWiki independent and free :)
World 4 is the fourth world contained in Super Mario 3D Land. This world is a pale green meadow with small, medium and large mushrooms. World 4 contains six levels and a Mystery Box. It is also the first encounter with Pom Pom, the boss of this World.
The two possible contents of this world's Mystery Box are: