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Märket
A bare Baltic skerry split between Sweden and Finland by a zig-zag border drawn around a lighthouse
Märket is a treeless lump of granite in the Baltic Sea, smaller than many city parks, yet it carries one of the strangest borders in Europe. The line between Sweden and Finland crosses the island not as a straight cut but as a crooked inverted S that doubles back on itself around a red-roofed lighthouse. The shape is the result of a quiet bargain between two friendly neighbors: Finland had built its lighthouse on the Swedish half by mistake, and rather than trade territory, the two countries redrew the line so each kept exactly the same amount of land. Nobody lives on Märket, and the only regular visitors are lighthouse enthusiasts and amateur radio operators.
The skerry lies in the Sea of Åland, midway between the Swedish coast of Uppland and the main islands of Åland, the autonomous Swedish-speaking Finnish archipelago. It measures about 350 meters by 150 meters, roughly 3.3 hectares, and rises only a few meters above the waves. The Finnish part belongs to Åland and is Finland's westernmost point of land, while the Swedish part is split between Uppsala and Stockholm counties. The border runs about 480 meters across the rock, linking the lighthouse to the rest of Finnish territory by a narrow strip. There is no harbor. Boats can land only in calm weather, and the nearest port, Berghamn on Eckerö in Åland, is about 23 kilometers away.
When Sweden ceded Finland to Russia in 1809, the Treaty of Fredrikshamn ran the new frontier through the middle of Märket. In 1885 the authorities of the Grand Duchy of Finland built a lighthouse on the island's highest point, which turned out to sit on the Swedish side. The error lingered for a century. In 1985 Sweden and Finland signed an agreement that bent the border into its current zig-zag, placing the lighthouse in Finland while keeping each side's area and coastline unchanged. The light was automated in 1979, and the old keepers' buildings stand empty. Märket remains a favorite of map lovers, a compact lesson in how borders can be adjusted by agreement rather than conflict.