Ertholmene

Ertholmene (formerly spelled Ærtholmene) is a small archipelago in Denmark. The largest island is Christiansø, whose name is often used with reference to the entire archipelago. Ertholmene are situated 18 kilometres (11 mi) northeast of Gudhjem, Bornholm, and include Denmark's easternmost point. Two of the islands, Christiansø and Frederiksø, are inhabited, with a combined permanent population (as of 2024) of 91. The archipelago has a total area of 39 hectares (96 acres). Its name is derived from the Danish for "pea islands".

Historically an important navy location, the fortress closed in 1855. Since then there has been no operable military infrastructure on the archipelago, but it remains under the formal administration of the Ministry of Defence, which employs 25 to 30 people for maintaining the islands' civilian infrastructure, museum and historical buildings. Today the economy of Ertholmene is almost entirely based on tourism, with tens of thousands of visitors each year, the majority on day-trips from Bornholm during the summer months. The archipelago's buildings and nature are protected by law, and access to the uninhabited islands is restricted.