During medieval times, Sigtuna boasted seven stone-built churches, though most have since crumbled. Mariakyrkan is the oldest brick building in the area – it was a Dominican monastery church from around 1250 but became the parish church in 1529 after the monastery was demolished by Gustav Vasa. Pop in for restored medieval paintings and free weekly concerts in summer.
The adjacent St Olof church was built in the early 12th century, but by the 17th century it was a ruin. Nearby, the ruins of St Per and St Lars can be seen off Prästgatan.