This Tiny Island Is Split Between Two European Countries (And You Can Walk Across The Border In Under A Minute)

You may have heard of some islands split between two nations. On St. Martin, a popular island that's a great base for hopping around the Caribbean, for example, you can walk from French cafés on the northern side owned by France to beach bars in the Dutch-owned south. These shared-border islands represent a history of negotiation and sometimes geographical absurdity. One of the most absurd island borders is on a tiny, windswept outcrop in the Baltic Sea called Märket Island. Though it's barely big enough for a lighthouse, the island is split between Sweden and Finland with a peculiar, bendy border, and it's often considered the smallest sea island divided between two nations.

Märket Island is remote and accessible only by boat. It's just over eight acres in size — about the size of four Manhattan city blocks — and is formally considered a skerry (a rocky reef). The island's split dates back to 1809, when the Treaty of Fredrikshamn established that the Åland archipelago in the Baltic Sea would be the territory of what was then Russian-controlled Finland. The agreed-upon divide crossed right through Märket Island and was originally a straight line. Then, in 1885, the Russians built a lighthouse on the island, which was slightly over the Finnish side of the border. The issue wasn't actually addressed until 1981 — by which point Finland had gained independence — and the two countries agreed to redraw the border, giving Finland the lighthouse and Sweden some extra rocky coastline in return. Every 25 years, the border is resurveyed, meaning it could shift even more in the future. There are no checks at the border, but since Sweden and Finland are in two different time zones, you'd technically be jumping back or ahead an hour within a few feet.

The climate around Märket Island is notably quite rough, and getting to the island is dangerous if the weather conditions aren't calm. When the weather is right, though, it's possible to sail to the island from the port of Käringsund, an archipelago village in Finland. To get to Käringsund, you'll first need to fly in from Turku, Finland's oldest city, known for its art and cuisine. The 30-minute flight lands in Mariehamn, from where you can take a bus to reach Käringsund in another 30 minutes. From Käringsund, the boat ride to Märket Island takes around 45 minutes. The easiest way to explore the island is to book a tour — Norrö Holiday Village offers tours that include the boat ride from Käringsund.

Once you're on the island, the Märket Lighthouse is the centerpiece. Now decommissioned, it was once an important measure to help boats safely navigate around this stormy sea. The lighthouse is maintained by Finland's Lighthouse Society, which welcomes visitors during the summer months. You might be able to climb the lighthouse tower for great views over the sea. Another thing to look for is the zigzagging border. Its only indicators are white markers, each with arrows designating where the next marker in the sequence can be found. As you trek the border, you'll see rocky tide pools with some grasses and might spot wildlife like seals or razorbills. If you want to explore more of Finland's unique island geography, head a bit farther north to the Kvarken Archipelago Nature Reserve, where kayakers thrive among its thousands of islands.