The small archipelago of Ertholmene consists of six rocky islands, but only two of them – Christiansø and Frederiksø are inhabited. Between the islands there is a natural harbor in which tourist ferries, yachts and small, private boats are moored. Traditional stone buildings of Christiansø blend perfectly with the natural features of the archipelago. On this 22-hectare island there are a lighthouse, a small hotel and campsite, primary school, church and a health care centre. What is more, there are also the remnants of the towers and defensive walls of the late 17th century.