A tiny European island nestled between northern Spain and southern France oddly flips nationalities every six months due to a unique three-century-old treaty struck between the two countries.

Pheasant Island, an uninhabited 660-foot-long spot in the Bidasoa River, bounces back and forth between the Spanish city of Irun and the French town of Hendaye, according to the area’s tourism website.

The twice-yearly handover, marked by a formal military parade, stems from the Treaty of the Pyrenees. 3

The unusual agreement, signed on Nov. 7, 1659, ended the Franco-Spanish War and established the desolate island as a border between the two nations — effectively placing the sliver of territory under Spanish control from Feb. 1 to July 31, and under French governance from Aug. 1 to Jan. 31.

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