What is it? In summer, the water bustles with sailboats and the islands that dot the inner Oslo Fjord – including Hovedøya and Gressholmen – are ideal for swimming, beach picnics and hiking.
Why go? It only takes five minutes by ferry to reach the main island, Hovedøya, with its lush forests, beaches and monastery ruins – and it costs just 38 NOK (the same as a bus). Buy a day pass, and jump from island to island, or book a guided tour.