A WWII gun platform in the North Sea declared itself its own country

HM Fort Roughs was built offshore in 1943 to defend Britain from air raids, then abandoned after the war. In 1967, a former pirate radio broadcaster occupied it and declared it the sovereign 'Principality of Sealand', complete with its own flag, currency and passports. No country recognises it, but it has survived coup attempts, fires and six decades of legal ambiguity.

— Bates family, Principality of Sealand — HM Fort Roughs, North Sea, occupied 1967