Laputa was a floating island above Venice, Italy. In 1609, Irving Braxiatel held a gathering of aliens on Laputa in order to create the Armageddon Convention. When he first heard the name, the First Doctor was confused, as he knew Laputa as the name of a fictional island in Jonathan Swift's Gulliver's Travels. (PROSE: The Empire of Glass [+]Andy Lane, Virgin Missing Adventures (Virgin Books, 1995).)
In the far future, Professor George Litefoot compared the Venusian floating city Amtor to Laputa. (AUDIO: Voyage to Venus [+]Error: Code 2 - no data stored in variables, cache or SMW.)
Behind the scenes[]
The name is one of Jonathan Swift's jokes; la puta is Spanish for "the whore".