Christiansø is the largest island of the Ertholmene archipelago, a cluster of tiny islands 18 km northeast of Gudhjem that marks Denmark's easternmost point. Together with neighbouring Frederiksø — linked by a short footbridge — it forms one of Europe's best-preserved sea fortresses, laid out in the late 17th century under King Christian V as a forward naval base in the Baltic. The fortress era ended in 1855, and today only around 90 people live permanently on the islands. There are no cars and only the most minimal shops; life follows the rhythm of the sea and the ferries. Visitors climb the Store Tårn tower for a panoramic sweep over the Baltic, wander the old ramparts and cannon batteries, and take in the island museum's account of the fortress's dramatic past. The buildings and surrounding nature are legally protected. Reaching Christiansø means a ferry from Gudhjem or Svaneke (about an hour), so it rewards an unhurried day-trip — take an early boat and stay for the quiet after the day visitors leave.
A local's tip
Take the first ferry and stay until the last - give yourself time to feel the island's special tranquility
Getting there
Ferry from Gudhjem (1 hour) or Svaneke. Book well in advance.
Best time to visit
May-September for best weather and ferry frequency
Accessibility
Uneven terrain and stairs - difficult for wheelchairs
