Christiansø is the largest of a cluster of granite islands, known as Ertholmene. Christiansø has a population of about 150 people and is connected to its smaller sister island of Frederiksø by a footbridge. There are no cars, modern buildings or domestic animals on Christiansø and the entire island is a reserve that includes a 17th century fortress.

The Store Tårn (Great Tower) in Christiansø was built in 1684. It has a diameter of 25 m and at the end of the 19th century a lighthouse was added to its top. From there you'll have excellent views over the island. You will also be able to see the nearby island of Græsholm, which is a wildlife refuge and home to large numbers of razorbill, guillemot and other seabirds.

On the eastern coast of Christiansø are numerous places where seabirds nest, as well as a nice swimming cove. Christiansø is an hour by boat from Bornholm, but they only sail from May to September. The mail boat runs all year round though. Christiansø is 160 km east of København (Copenhagen).