Kalvøysund is a village in Arendal municipality in Agder county, Norway.

The fortress included 50 bunkers and other buildings and 4 emplacements for artillery.

After WW2 ended and Norway liberated, the Norwegian armed forces used it for military exercises.

Now it is in the possession of the local authorities and is a tourist destination.

“Kalvøysund Fort.” Visitnorway, Innovation Norway, 20 Sept. 2020, https://www.visitnorway.com/places-to-go/southern-norway/arendal/listings-arendal/kalv%C3%B8ysund-fort/7064/.