Hovedøya Island is a nature reserve and historical site in the Oslofjord, just a 10-minute ferry ride from the city center. The island is home to Norway's best-preserved medieval monastery ruins - a 12th-century Cistercian monastery built by English monks. The island features swimming beaches, dense forests, and walking trails. It's a perfect escape from city bustle with barbecue facilities in designated areas. Ferries run year-round from Aker Brygge and accept regular Oslo public transport tickets.