The first ”capital” of Sweden
Näs is the oldest royal castle in Sweden. The castle was built in the middle of the twelfth century to serve as an impregnable fortification during feuds between the dynasties of Sverker and Erik. The location is strategically chosen on a point of view in all directions. During the twelfth and the thirteenth centuries the kings often stayed in Visingsö.
Here in 1167 Karl Sverkersson fell victim of its rivals for power. Several other medieval kings died here: Erik Knutsson (heated fever), Johan Sverkersson (died a natural death), Magnus Ladulås (illness).
During the fightings between the sons of Magnus Ladulås the castle burned down in1318.
Over the centuries much of the castle has been eroded by the lake Vättern.
The great Icelandic storyteller Snorre Sturlasson has visited Näs and the court of Johan I. In the Icelandic saga Rimbegla he speaks of Visingsö and "its considerable palace where the king keeps his treasures, and which is the strongest in the kingdom."
The treasury was probably the round, vaulted room in the east tower, accessible only through a hole at the top of the dome.