An island in Lake Vättern holding Näs, the earliest known royal castle in Sweden, where four kings of the Sverker and Erik houses died between 1167 and 1290.
Visingsö lies in the southern part of Lake Vättern, about thirty kilometres north of Jönköping and six kilometres out from Gränna on the eastern shore. It is long and narrow — some fourteen kilometres by three at its widest, about twenty-four square kilometres in all — and it sits in open water in the middle of one of the largest lakes in Europe.
That position made it a natural seat of power in the twelfth century. At the southern tip stood Näs, the earliest royal castle known in Sweden, and for something like a century and a half the island was as close as the kingdom came to having a fixed centre of government.
Vättern is deep, cold and frequently rough, and Visingsö is far enough from either shore to be genuinely difficult to reach without boats — which is the whole point of putting a castle and a treasury on it. An island stronghold in the middle of a great lake could not be rushed, blockaded cheaply, or taken by a raiding party, and in a kingdom whose politics consisted largely of two families murdering each other, that mattered.
The island sat centrally in the medieval kingdom, at the meeting point of Östergötland, Småland and Västergötland, so it was defensible without being remote from the provinces that made a Swedish king.
Näs was built during the twelfth century; the most likely builders are Sverker the Elder, who reigned from about 1130 to 1156, or his son Karl Sverkersson. It is called Sweden’s first riksborg — the first castle of the realm rather than of a lord — and it served as the royal treasury as well as a residence, which is to say it held the things a king could not afford to lose.
The remains measure roughly thirty-two by twelve metres and include the footings of a round tower and a four-sided one. The walls, of slate and sandstone, still stand three to four metres high and are between one and one and a half metres thick, with sockets visible for the joists of an upper floor. It is not a large castle by later standards, but in twelfth-century Sweden it was a stone building of a kind almost nobody else had.
Näs has a remarkable record: four Swedish kings died there. Karl Sverkersson was killed on the island in 1167 by supporters of his rival and successor Knut Eriksson. Erik Knutsson died there in 1216, Johan Sverkersson in 1222, and Magnus Ladulås — Magnus III — in 1290.
The sequence tracks the long feud between the houses of Sverker and Erik, which alternated on the Swedish throne for more than a century, and it shows what the castle was for. A king stayed where he could not be surprised; when he was old or ill, he went to the strongest place he had. The one king who was murdered there died because the island’s security failed him, not because it was a soft target.
The castle’s end came in 1318, when Birger Magnusson pledged it to the Danish king during the civil war against his brothers, and it was burned after fighting in the same year while he was in exile. It was never rebuilt, and the centre of Swedish royal power moved north to Stockholm.
The island’s second castle belongs to a different era. Visingsborg was built from the 1560s and became the seat of the Brahe family, who held Visingsö as a county in the seventeenth century and ran it as a small dynastic capital with a school and a printing press. It burned in 1718, during the Great Northern War, and its ruins — not those of Näs — are the ones that dominate photographs of the island today.
Kumlaby church, the medieval parish church in the middle of the island, also survives. For the archive the useful point is the distinction between the two ruins: the famous one is early modern, and the one that matters to medieval Swedish kingship is the low walling at the southern end.