Oscarsborg Fortress

Norway, Norway

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Oscarsborg Fortress is a historic coastal defense installation on Kaholmen island in the Oslofjord near Drøbak, Norway, originally established in the 1640s under King Christian IV with early blockhouses and batteries to protect the capital from naval attacks. Upgraded in the mid-19th century into one of Northern Europe's strongest fortresses—featuring main forts, casemates, 28 cm Krupp guns named Moses, Aaron, and Joshua, plus submerged torpedo batteries like Kaholm and Bloksberg—it played a pivotal role on April 9, 1940, by sinking the German cruiser Blücher, delaying the Nazi invasion and allowing King Haakon VII and the government to escape. Decommissioned in 1999, it now serves as a museum, hotel, and cultural site with guided tours of tunnels, batteries, and WWII exhibits amid scenic fjord surroundings.