Oscarsborg Fortress is a jewel in the Drøbak narrow. In summer, Oscarsborg is perfect for families and for those interested in nature, culture and history. Oscarsborg Fortress Museum presents the history of the place and organises guided tours. There are plenty of activities for children. A safari through the subterranean tunnels below the fortress, obstacle courses, bathing beaches and crab fishing.The unique surroundings of the fortress provide a fantastic arena for the theatre, opera and concerts which are organised during the summer season. At Oscarsborg you will find an art gallery, exhibitions, Spa and a good selection of places to eat. In summer you can travel by ferry from Drøbak and Oslo, or arrive with your own boat to Oscarsborg Marina.HistoryAkershus Fortress had been the defender of the capital Oslo/Christiania for hundred of years. In the sixteenth century there was a great deal of unrest in Europe and it became important to have a fortification further out from the capital. The Drøbak Sound was identified as a strategic position for defence. In 1640 King Christian IV in Copenhagen ordered a blockhouse to be built on the Southern Kaholmen, which was finished in 1643.The state bought the two Kaholmen Islands in 1845. The planning began immediately and the construction works started in 1846. After the visitof King Oscar in 1855 the fortress was given the name Oscarsborg. However, already in the 1860’s the fortress was out of date, developments in artillery had been rapid and the technical revolution had created a transformation in the way warfare was conducted.Originally the fortress Oscarsborg was created to resist attack from sea and not over land. To withstand attacks over land the fortress was extended from 1890. New gun batteries were placed on Kaholmen, Håøya and on both sides of the fjord. An underwater stone wall (jeté), minefield, torpedo battery and entrenchments was also built.When the negotiations with Sweden took place in 1905, the Oscarsborg fortress was regarded as the strongest fortress in northern Europe, with a defensive line that stretched 10 km from the HeerEntrenchment in the east to the top of Håøya in the west.On the 9th of April 1940 Oscarsborg Fortress endured its first real trial. The fortress delayed the German attack by sinking the heavy cruiser “Blücher”; the newest cruiser of Germany. This slowed the attack, which gave the King, Government and Parliament sufficient time to evacuate Oslo and later on take up the fight against the occupation of Norway.After the Second World War the strategic importance of Oscarsborg reduced and the last fortification was ended on the 1st of January 1993 and in 2002 the fortress became finally abolished.In 2004 the Parliament decided to create The National Fortifications Heritage(“Nasjonale festningsverk”) which has the responsibility for the maintenance of 14 historical fortresses, among them Oscarsborg Fortress.Cultural arenaOscarsborg is a unique cultural arena for opera and concerts throughout the summer season. This year has an exciting programme with an acoustic pop/rock festival, wandering theatre troupes and fantastic opera experiences in the courtyard throughout August – just to mention a few. Oscarsborg has an art gallery run by Avistegnerne in Drøbak. “Forsvarets Hus” (“Military House”) in Kommandantboligen shows how the Norwegian military is today.