Pheasant Island, a small territory on the Bidasoa River, continues its tradition of swapping national flags every six months [1].
This arrangement preserves one of the world's rarest forms of joint administration, known as a condominium. The practice serves as a living reminder of how early modern diplomacy settled territorial disputes through shared sovereignty rather than permanent division.
Located on the border between France's Pyrénées-Atlantiques and Spain's Guipúzcoa, the island sits near the towns of Hendaye and Irun [1]. The current administrative structure is rooted in the 1659 Treaty of the Pyrenees [1]. This historic agreement designated the land as a neutral zone to resolve conflicts between the two nations.
Under the terms of the treaty, the island does not belong exclusively to either country. Instead, the two nations share control, and the national flag is changed twice a year [1]. Each period of administration lasts for six months [1].
This alternating sovereignty ensures that neither France nor Spain maintains a permanent military or political advantage on the river island. The process remains a diplomatic formality that has survived for centuries, a rare instance of a 17th-century border agreement remaining active in the modern era.
While the island is tiny, its status as a condominium makes it a unique geographical anomaly in Europe. The periodic transition of the flag marks the official shift in administration, maintaining the delicate balance established by the 1659 treaty [1].
“The national flag is swapped every six months as part of a French‑Spanish condominium arrangement.”
The continued administration of Pheasant Island demonstrates the longevity of international treaties in defining European borders. By maintaining a neutral condominium rather than a hard border, France and Spain uphold a diplomatic precedent that prioritizes shared cooperation over exclusive territorial claims.
