Photo: Kjetil Lenes·CC BY 2.5· Wikimedia Commons
Islands / Frogn / Søndre Kaholmen
The main island of Oscarsborg fortress, with the main fort from 1848. Today it is a national fortress site with a museum, hotel and restaurant, and the stage for the Oscarsborg opera every August. Around 100,000 visitors a year.
The main island at Oscarsborg, the one with the big white fort and the guns pointing out across the sound. This is where the shots at the Blücher were fired from, and where the hotel, the restaurant and the opera stage are today.
Ferry from Drøbak, year-round.
Times shift with the season, and several of the island boats run only in summer — check the current timetable at Ruter.
The main fort on Søndre Kaholmen was completed on 20 November 1848 and carried more than 100 guns by the 1850s. It was modernised from 1875 and extended between 1893 and 1901. Its armament included three 28 cm Krupp guns named Moses, Aron and Josva.
On the morning of 9 April 1940, commandant Birger Eriksen gave the order to fire on the German cruiser Blücher without a warning shot. Two of the big guns opened fire at close range at about 04.21. Together with the torpedoes from Nordre Kaholmen they sank the Blücher, with around 1,000 men aboard. The delay gave the royal family, the government and the national gold reserve time to get out of Oslo.
Søndre Kaholmen is the core of what is now a national fortress site, protected as a cultural monument since 9 May 2014. The Norwegian Armed Forces Museum keeps a department here, and there is a hotel with around 190 beds, a restaurant and galleries. The Oscarsborg opera is staged here every August on the fortress grounds, with the fjord behind it. Around 100,000 people visit Oscarsborg a year. The fortress was decommissioned as a military installation on 28 June 2002.
The ferry from Drøbak runs all year. Your own boat can tie up in the guest harbour. The museum and the outdoor areas are open to the public; the hotel and restaurant are run commercially, and the opera requires a ticket.
The three guns were called Moses, Aron and Josva: biblical names on German-built Krupp guns that were used against a German cruiser.
The opera audience now sits where gunners loaded shells in 1940.
The fort is nearly 180 years old and stayed in military use until 2002.
Oslo Sea Experience passes Søndre Kaholmen on its private fjord trips from Tjuvholmen.
The Norwegian version notes which facts were taken from each source: Søndre Kaholmen på norsk.