Laputa.
Laputa is a legendary flying city, once hosting a very powerful civilization before it mysteriously vanished. Most of people of the Earth view the tale as a myth, although some have insisted to have proof of its existence, such as Pazu's father.
Etymology
The name for Laputa was derived from Jonathan Swift's famed book Gulliver's Travel, which also featured a floating city named Laputa as well.
The word Laputa has negative meaning in Spanish language, where "La Puta" essentially means "The Whore."