The Cistercian monastery, also known as Hovedøya monastery, is located on Hovedøya in the Oslofjord. The monastery was founded in 1147 by the Cistercian order and is one of the oldest monasteries in Norway. The buildings are an example of medieval monastic architecture, and the facility has been the subject of several archaeological investigations which have uncovered important historical layers.
The monastery was originally built to house monks who lived by the strict rules of the Cistercians, which focused on prayer, work and community. Today, the ruins of the monastery are a popular destination for tourists and locals alike, and the site is known for its scenic location and historical significance. The area around the monastery also offers opportunities for recreation and outdoor life, which makes it an important part of Oslo's cultural heritage.