Floating island (fiction)
A floating island in fiction is a landmass that floats in a body of water (such as Vadanis in The Guardian Cycle of novels), or in the sky (such as Angel Island from Sonic The Hedgehog), when it could be considered a flying island, such as the flying continent of Laputa in Castle in the Sky. They can be free-floating, may be directed by the whim of their inhabitants, or others may be permanently anchored.
Floating islands have been found in literature since Homer's Odyssey, written near the end of the 8th century BC. They reappear in Pliny the Elder's Natural History of the 1st century AD, as the island of Laputa in Jonathan Swift's 1726 book Gulliver's Travels, and many times in more recent works.
Floating islands may be held aloft by lighter-than-air gases, such as helium or hydrogen; a lodestone, magnet, crystal, or other mineral; magic; levitation technology such as anti-gravity, propellers or balloons.
One example, of the latter, is the famous floating island, Mt. Flatten, from the TV cartoon series Rocky and His Friend. Mt. Flatten is held aloft by an ultra-rare, anti-gravity metal, aptly named Upsidaisium. The only source of Upsidaisium is the ore from Bullwinkle's mine on Mt. Flatten.