Götlunda (10km from Arboga) has remaines from the 11th Century which features a rune stone called Kung Sigges sten (King Sigge’s stone). Between Arboga and Götlunda is the ancient castle Halvardsborg, which is one of three in the parish of Götlunda. Arboga’s town centre was already developing into a busy community in the 11th Century, with the first of five churches, St Nikolai’s, being completed 100 years later.
An exciting period in Arboga’s history was when the Franciscan monks settled here during the 13th Century; Gråbröderna (the grey brotherhood), as there were called, were known for participating in communities which they thought had the potential to expand and develop. This was true of Arboga and the town owes a lot to the work of the monks, e.g. the monastery they built which later became the church of the Holy Trinity in Arboga. The monks also tended to the poor and the sick as well as teaching reading skills to children. There are many stories of an old network of underground passages in which the monks could move around the town in secret. The monks stayed in Arboga until the 16th Century, when King Gustav Vasa broke with the Roman Catholic Church, took over all the monasteries and drove the monks out of Sweden.