As part of Medieval Oslo, the park contains the ruins of Oslo's first- cathedral, the Hallvard's Cathedral, as well as the Olav's Monastery and the Church of the Cross.
The Hallvard Cathedral was built in the early 1100s as a Romanesque basilica, with a central tower and transept. The church was used until 1660, and the last remnants of the building was demolished around 1780. The Olav's Monastery (Dominican Order), built in 1240, was a conversion of the former St. Olav's Church.
The Church of the Cross was a small parish church for the northern part of the city. The ruins show the outline of the church, and the lower parts of the south doorway. You can see the remains of the shrine foundation, and the remains the cemetery wall surrounding the church.
Officially opened in 1932 the park's main attraction was the ruins of St. Halvard Cathedral. In the 1960s a concrete cover was placed over the southern part of the park for the benefit of a road.
Photo: Helge Høifødt / Wikimedia Commons