Skylands

This Dimension Does Not Exist Anymore, was removed in March 2012

The Skylands was a dimension of floating islands.

To go there, you needed to make a Glowstone portal that you lit with a flint and steel. This dimension was practically empty of players since there isn't much to get from it. It had regular overworld blocks and mobs. Chickens were more prevalent there. Floating islands made up the terrain, and contrary to popular belief, falling into the Skylands void will NOT put you in the Overworld, instead you took damage until you died or warped out.

Removal

The Skylands, along with the Swamp World (Swamplands), has been removed. Portals leading to there will message you that the dimension cannot be found.