Christiansø Museum

The museums of Christiansø — part of the Ertholmene archipelago northeast of Bornholm — comprise the island's two historic fortress towers (Store Tårn and Lille Tårn) and the Ballon prison cell on Frederiksø. The towers are open daily, with hours that follow the Christiansøfarten ferry schedule, and the Ballon (a state prison built in 1825 to hold philosopher and political dissident Dr. Jacob Jacobsen Dampe for 15 years) is freely accessible year round, with a small exhibition about Dampe on the first floor. The fully protected island group preserves Denmark's fortress, fishing-community and natural heritage in one place.