After the Second World War

During the Cold War Oscarsborg formed a last line of defence for Oslo, with the underground torpedo battery remaining secretly active up until 1 January 1993, having been modernized in the 1980s.

After the deactivation of the last weapons systems, the remaining military activity on Oscarsborg consisted of the Coastal Artillery officer training programme. The officer school was officially shut down on 28 June 2002.

The fortress is now largely a civilian resort and attraction, open for visitors. Parts of the former fortress are used as a hotel resort. The scenic surroundings is much used for conferences and excursions. Visitors take a short motor launch trip from Drøbak.

On 8 April 2014 the 28 cm guns of the main battery were fired with blank rounds when the fortress was used as a location of a scene for the production of the 2016 film The King\’s Choice, directed by Erik Poppe. In their coverage of the filming the newspaper Aftenposten claimed that the filming occasion was the first time the guns had been fired since 9 April 1940. The claim by Aftenposten is however contradicted by the fact that the guns were actually last fired during testing in 1952.

After a prolonged process, Oscarsborg Fortress was listed as a protected site in 2014, effective from 9 April 2014.