Tynnelsö Castle, Medieval castle on Tynnelsö island, Lake Mälaren, Sweden
Tynnelsö Castle is a stone fortress located on an island in Lake Mälaren, situated northeast of Strängnäs. The building features a square layout with multiple stories and appears as a solid fortified structure rising from the water.
Tynnelsö is first mentioned in 1282 and belonged to the Diocese of Strängnäs from 1306. The oldest stone house was probably built at the end of the 14th century under Bishop Tord Gunnarsson, and in the 1490s Bishop Kort Rogge built the stone house that forms the castle's lower floors. Duke Charles added the two tower-like extensions in the 1590s.
The castle served as a strategic military fortification in 1443, housing 24 firearms, multiple cannons, and an arsenal of crossbows.
The castle is managed by the Swedish National Property Board (Statens Fastighetsverk), which took over from the National Heritage Board in 2015. In January 2025 it was put up for sale. As a first step in a planned renovation, the roof lantern has been restored and the foundations inspected; the interior remains closed while work continues.
During Bishop Sigge's leadership from 1449 to 1463, the castle maintained a garrison of 100 men, making it one of Sweden's strongest fortifications.
The community of curious travelers
AroundUs brings together thousands of curated places, local tips, and hidden gems, enriched daily by 94,839 contributors worldwide.
