The Sörmland Museum belongs to the Swedish county of Södermanland and conducts historical and archaeological research throughout the region. You can see, among others a permanent exhibition showing the fate and character of the medieval city of Nyköping.
The museum exhibition is located in a historic castle (Nyköpingshus) built in the Middle Ages. Photos and historical exhibits can also be seen in other parts of the county, they are located along tourist routes, incl. in barns.
The castle is famous for the events that took place in 1317. A sumptuous banquet was held here, which ended very unhappily. The princes Erik and Valdemar Magnusson were invited to it, while the magnate, Birger Jarl, worried about his future, betrayed them and ordered their capture. They were starved to death.