There's a tiny island on the border between France and Spain where it is possible to go to sleep in one country, not move an inch, and wake up in the other. Well, it would be possible if it were legal to visit the island, but alas, at less than 75,000 square feet, it is smaller than some grocery stores and off limits to the many feet that would otherwise pound it. So how does this travel-without-moving work? As Conde Nast Traveler explains, it has nothing do with geography and everything to do with an unusual deal between France and Spain that goes back four centuries. In short, they swap control of the island during the year.
The island, which the Spanish call "Isla de los Faisanes" and the French call "Île des Faisans," has been jointly run by the two countries since the Treaty of the Pyrenees was signed there in 1659. The terms created what is essentially joint custody, by which the Spaniards have control from February to August, and the French from August to February. It's one of the most unique border arrangements in the world, notes a post at Atlas Obscura, which calls it "a powerful, albeit bizarre, symbol of peace and neutrality." The island's history is rather romantic, if that's the right word, given that it used to be where brides and grooms of royal marriages between the countries were handed off. (See why Japan is spending so much on this tiny island.)