World__57.zip is a release file of the Minecraft map World #57 Now Available for Habitation!, made for Minecraft 1.7.4. It was published on March 9, 2014 and is 49.3 MB in size. For the full description, screenshots and every other version, visit the World #57 Now Available for Habitation! map page.
How to install: Extract the .zip and move the world folder into .minecraft/saves; the map then appears in your Singleplayer list.