Oscarsborg Fortress, Coastal fortress in Oslofjord, Norway
The fortress spans across two small islets, Nordre Kaholmen and Søndre Kaholmen, with additional artillery batteries on Håøya island and the mainland.
The fortress delayed the German invasion of Oslo in April 1940 by sinking the heavy cruiser Blücher, providing crucial time for Norwegian leadership evacuation.
The Oscarsborg Fortress Museum presents military exhibitions while the grounds host theater performances, opera shows, and concerts during summer months.
Visitors can reach the fortress via regular ferry services from Drøbak or Oslo, with options for guided tours through the underground tunnel system.
The fortress maintained a secret torpedo battery with an underwater launch system that remained unknown to German intelligence during World War II.
Location: Frogn Municipality
Inception: 1848
GPS coordinates: 59.67361,10.60667
Latest update: May 27, 2025 07:00
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