Answer: When that floating island is a gigantic polyurethane balloon filled with helium. It's an art project called Is Land and has trees and foliage decorating it to make it seem like a floating island. But it's gone!
The 23-foot scuplture cost around $15,000 and took six months to build. Sarah Cockings and Laurence Symonds, Royal College of Art graduates, had tied the sculpture down at the Secret Garden Party in Cambridgshire, UK with intents of bringing it to Burning Man in Black Rock City, Nevada. Their plans were thwarted when some jackasses thought it funny to cut the rope and let the floating island free.
Cockings and Symonds have no idea where Is Land is but atmospheric data point that it may be hovering somewhere over the Czech Republic. Planes have yet to run into the balloon but some people have reported UFO sightings similar to Is Land's shape so there may be hope still. If they don't locate Is Land, they're still trying to build another in time for Burning Man. As the world needs more floating islands, I'd wouldn't mind that. [Is-Land via Neatorama, Image Credit: Nick Caro]