Sigtuna was founded to be the first Christian town in Sweden – the center of the new religion. St. Lawrence Church was built around 1100–1200. It was probably a large building of at least 25 meters. Today, you can see the remains of the tower and parts of the northern wall.

During the Middle Ages, as many as seven large stone churches were erected by merchant guilds and wealthy townspeople. Today, the ruins of three remain: St. Peter’s, St. Lawrence’s, and St. Olaf’s (S:t Per, S:t Lars, and S:t Olof).