The ruins of St. Mary's Church are a historical landmark located in Oslo. This site is the remains of a medieval church that was built in the 12th century. The church was part of the Catholic church system until the Reformation, and it has been an important symbol of Oslo's religious and cultural history.
The ruins give an insight into the architectural style from the Middle Ages, with characteristic features such as thick brick walls and arched windows. Today, the area around the ruin is a popular destination for both locals and tourists who want to learn more about Oslo's history. The ruins of St. Mary's Church are also an important archaeological site, where several discoveries have been made that give insight into life in Oslo in earlier times.