Ertholmene: Natural Beauty and Fortress History

When looking for a hotel for a trip to Ertholmene, you should also consider the time of year when planning: Christiansø can only be reached by ferry, and services vary by season. Here, a history as a naval fortress meets a varied landscape and diverse birdlife.

Getting There and Seasonal Ferry Services

Christiansø can only be reached by the Christiansø Ferry. It departs from Gudhjem harbour, and the crossing takes about an hour. During the high season, the Ertholm ferry runs up to three times a day. In winter, the mail boat Peter runs twice daily on weekdays. Service frequency may change, so check the current timetable before travelling. The differences between the high season and winter are an important planning consideration when coordinating your travel dates and stay on Ertholmene.

Fortress History and Museums

The natural harbour between Christiansø and Frederiksø was the reason King Christian V chose Ertholmene as the site of his naval fortress in 1684. The two distinctive towers recall this original defensive purpose: Store Tårn stands on Christiansø, and Lille Tårn on Frederiksø. Both were built as key parts of the fortress and now house museums.

Store Tårn, with its integrated lighthouse dating from 1800, was completely renovated from 2014 to 2018. At Lille Tårn, exhibitions explore local military and cultural history. Those looking to understand the fortress’s construction history will find two different points of interest: the lighthouse in Store Tårn and the historical exhibition topics in Lille Tårn. Palivaren is also located at Juuls Bastion on Christiansø. During the summer season, artists exhibit and sell their works in this gallery.

Landscape and Birdlife

On Ertholmene, windswept rocky coast, shady woods and gardens alternate within just a few hundred metres. The birdlife is equally varied: thousands of eider ducks nest on the inhabited islands, even beside busy roads. Many migratory birds visit the islands in spring and autumn, including cranes and goldcrests.

A total of 302 different bird species have been observed on Ertholmene, and this number may rise as further observations are made. Breeding birds are counted separately: over time, 52 breeding bird species have been recorded, but only 25 species breed regularly on the islands. This distinction helps differentiate observed species from those that breed regularly, without treating the two figures as equivalent.

Græsholm is closed to the public and is home to one of Denmark’s largest seabird colonies. The birds can be observed with binoculars from Frederiksø. Up to 400 grey seals were reported resting on Ertholmene in 2013; the island group is one of the largest haul-out sites for this species of seal. This figure refers to the 2013 report, not to the current population.

Smaller habitats are also part of the natural environment: numerous ponds are home to amphibians, including toads, newts, the rare natterjack toad and the moor frog. Ertholmene is also a protected area for the Nordic honey bee. In 2020, Christiansø was designated an official nature reserve by the Danish Outdoor Council. Earlier, in 2018, Ertholmene was included as one of 15 places in the Kingdom in Denmark’s Nature Canon, the official list of Denmark’s most beautiful places.

For the broader travel overview: Denmark.