Memorial park in the Old Town with ruins of some of medieval Oslo's most important buildings. The park is open to the public.

St. Olav's Monastery from the 13th century is the best-preserved town monastery in the country. The old rooms inside are only accessible as part of a guided tour or in connection with events.

Next to the monastery are the ruins of the St. Hallvard's Cathedral, a grand church dedicated to Oslo's patron saint, built around the year 1070 AD. Oslo ladegård offers guided tours of the medieval town.