Four of Denmark's seven medieval round churches (rundkirke) are located on Bornholm. The round churches were used as fortresses, as well as places of worship, and the fact that such a high concentration of them are found on Bornholm, is testament to the island's strategically important location in the Baltic Sea.
The round churches are striking whitewashed buildings, with upper stories designed to double as shooting galleries against enemy attack. The largest round church is in Østerlars, with others found in the villages of Olsker, Nylars and Nyker.
All four churches are still used for Sunday services and are open to the public from Monday to Saturday.
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