World 1 (Super Mario 3D Land)
From the Super Mario Wiki
World 1 is the first world in Super Mario 3D Land. It takes place in a green field with flowers, pipes and hills in the background. It features five levels, a Mystery Box, and a Toad House. As the start of Mario's adventure, the levels of World 1 are rather basic.
This world reappears as a background for Dream Figure Skating in Mario & Sonic at the Sochi 2014 Olympic Winter Games.
The six possible contents of this world's Mystery Box are: