Portsmouth is a port city in Hampshire, England, with a total population of 205,400 residents. The city of Portsmouth is nicknamed Pompey and is mainly built on Portsea Island, a flat, low-lying island measuring 24 square kilometres (9 sq mi) in area, just off the south-east coast of Hampshire. Portsmouth is the only island city in the United Kingdom, and is the only city whose population density exceeds that of London.