Few nautical miles northeast of Bornholm, the Ertholmene archipelago – three small islands (one of them Christiansø) only two inhabited – feels like Denmark’s smallest and most charming “real” destination: a fortified rock, a compact harbour and just enough services to make a stop comfortable without losing that remote-island edge.
The main islands, Christiansø and Frederiksø, are connected by a small bridge. You can walk the whole place in an hour, but it rewards a slow pace: granite, greenery, fortifications, old guns, bright flowers and seabirds everywhere.
“ø” – is actually a full word in Danish, meaning “island”
Harbour & mooring
Christiansø’s harbour is small and well protected, shaped by the island’s defensive history. Space is limited. Boats are moored alongside the pier and in high season you may find yourself in 3–4 rows of boats rafted side by side. A practical mindset here: arrive with patience (and fenders ready), expect rafting, rig your lines so you can exit without drama when someone in the “inner row” needs to leave.
Ferry traffic: the island “breathes” during the day
Ertholmene is inhabited year-round, but only by a very small community (often quoted around 80-100 people, varying by year). In summer, that quiet baseline changes fast: the ferry from Bornholm can run 2-3 times per day. The harbour and paths get busy for a couple of hours – then the islands “exhale” again when day visitors leave.
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A bit of history
Built to be strategic Christiansø and Frederiksø were not built as a leisure destination. In the late 17th century Denmark created a fortified base here to control sea lanes and strengthen defence in the Bornholm area. The harbour layout, heavy stonework and compact streets make more sense once you remember the islands were a naval stronghold first and a civilian place later.
The islands also saw real action. During the Napoleonic era, British forces attacked Christiansø in 1808 – the one battle story everyone ends up hearing about.
The towers and the museum: history you can “see”
Both main towers now house exhibitions. Store Tårn (Big Tower) is the big landmark, renovated in recent years and it hosts permanent exhibitions on local history and nature. A highlight is a digital animation of the British attack in 1808 – an interactive retelling that’s popular even for people who are not museum types.
Denmark’s first flashing lighthouse Christiansø Fyr is mounted on top of Store Tårn. It was designed by Danish naval engineer Poul de Løvenørn and first lit on 1 October 1805 – notably as Denmark’s first flashing lighthouse, using Fresnel lenses -meaning a much brighter, more efficient beam and a clearer light signature for navigation.
Wildlife: seals on a slow schedule
One of the best “do nothing” activities here is simply watching wildlife. The waters around Ertholmene are known for grey seals, and you can often spot them resting and living their unhurried seal life. It fits the place: you came here to slow down anyway.
Fishing: what you might catch
Around Christiansø you can get lucky with garfish. Expect a long, needle-like body and a clean taste – and the classic “surprise”: the bones can look green. That’s normal for garfish and doesn’t mean the fish is spoiled. It’s a solid eating fish when cooked fresh.
Why it’s worth the stop
Christiansø is one of those destinations that is genuinely practical for a visiting yacht -a real harbour, a real settlement, a place you can comfortably spend a night – and it still feels like a remote outpost: minimal, maritime and shaped by history.
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