The Principality of Sealand
Wikipedia's entry
about Sealand.
The Principality of Sealand is a micronation that claims as its territory Roughs Tower, a derelict man-made structure located in the English Channel six miles (10 km) off the coast of Suffolk, England, at 51° 53′ 40″ N 1° 28′ 57″ E. It is occupied by the family and associates of Paddy Roy Bates. The population of the facility rarely exceeds five, and its inhabitable area is 550 mē.