On the Bidasoa River, which marks part of the border between France and Spain, sits Pheasant Island. This uninhabited strip of land is jointly sovereign territory, but responsibility for administering it changes hands twice a year: Spain takes charge from February 1 through July 31, and France from August 1 through January 31.
How the rotation works
The arrangement is known as a condominium, meaning two nations share sovereignty over the same territory. Crucially, Pheasant Island does not become exclusively Spanish or French at each handover; only its administration rotates. Officials responsible for policing, maintenance, and stewardship change, while the centuries-old agreement remains intact. It is the world’s smallest condominium.
This unusual system grew from the island’s role as neutral diplomatic ground. The Treaty of the Pyrenees, which ended a conflict between the two kingdoms, was signed there on November 7, 1659. Later agreements clarified the island’s shared status and alternating jurisdiction. A monument still recalls the peace negotiations.
Today the island has no residents, houses, shops, or border checkpoint. It lies close enough to both riverbanks to be seen, yet public access is generally restricted. Authorities in Irun and Hendaye handle its care, including controlling vegetation and protecting the river-worn banks.
Why the island matters
Pheasant Island is less a tale of territory being traded than an example of cooperation. Every February and August, administration changes without residents changing nationality or businesses switching laws, because there are neither. The ritual shows how an old border dispute can become a shared responsibility.
Its scale makes the story memorable. Compare it with Monaco, which is smaller than New York City’s Central Park. Pheasant Island, however, is remarkable not for statehood or wealth, but for proving that two countries can share a patch of earth on a calendar.