Big Tower (Great Tower) on Christiansø

Sea Fortress Sentinel Above the Baltic

The Big Tower, often called the Great Tower, dominates the low profile of Christiansø, a tiny rocky island far off Bornholm’s northeast coast. Completed in the late 1600s as part of the Ertholmene sea fortress, it was built to watch over one of Denmark’s most strategic stretches of water. Massive stone walls, narrow openings and sturdy foundations still speak of a time when enemy ships and privateers were a real threat, and this remote outpost formed a shield for the kingdom.From the outside, the tower’s rounded bulk rises directly from the granite landscape, surrounded by ramparts, bastions and neat lines of yellow and red houses. The proximity of the sea is constant: gulls circle overhead, wind rattles rigging in the small harbour, and the salty tang of the Baltic reaches right up to the tower’s entrance.

From Lighthouse Beam to Modern Renewal

In 1800 the Big Tower gained a new life as a lighthouse, guiding ships instead of defending against them. The lantern once threw its beam far across dark water, helping captains steer safely past reefs and shoals. When the naval fortress closed in the 1850s and the military presence faded, the tower slowly deteriorated, its interior ageing along with the rest of the former stronghold.A major restoration completed in 2017 transformed the structure without erasing its history. Today, the interior feels bright and carefully modernised, with discreet fittings and exhibition spaces set against bare stone. As you move between levels, you sense both the weight of centuries and the island’s decision to keep the tower as a living part of community life rather than a frozen relic.

Exhibitions Inside the Old Walls

Within the tower you find changing cultural events, art shows and historical displays that interpret Christiansø’s past as a naval base and later as a small, tightly knit island society. Exhibits may explore life in a garrison town, the evolution of lighthouses, or the strategic importance of this easternmost outpost. Text, objects and atmospheric lighting all work within the curved masonry, creating an intimate feeling quite different from large mainland museums.Spaces are compact and linked by relatively steep stairs, a reminder that this was never designed as a public building. Narrow embrasures frame glimpses of the sea, while thicker interior walls hold traces of older fittings and adaptations. Even during an event or concert, you remain aware that you are standing inside a centuries-old defensive core.

Views Across a Living Island Fortress

Climbing higher, the tower gradually reveals the layout of Christiansø and neighbouring Frederiksø. From the viewing levels you look down on complete 17th- and 18th-century fortifications, stone cottages, half-timbered houses and the sheltered harbour that links the two islands by a short bridge. Beyond the walls, the Baltic stretches towards the horizon, sometimes glassy and pale, sometimes dark and wind-streaked.On clear days, the contrast between the green interior gardens, rocky shoreline and open sea is striking. Cannons still line some bulwarks, and you can pick out the Little Tower on Frederiksø, which houses the island’s museum. The setting feels surprisingly self-contained: a miniature society with its own school, guesthouse, workshop yards and busy harbour, all clustered around the same stronghold that once guarded the realm.

Part of a Protected Nature and Heritage Haven

The Big Tower stands within a protected area where fortress remains, village structures and surrounding wildlife all enjoy special status. The Ertholmene archipelago is state-owned and overseen as a heritage and nature reserve, and the islands host large bird colonies and frequent seal sightings just offshore. Walking between the tower and the shoreline, you move from thick walls and cobbled paths to low heather, grasses and sea-exposed rocks in just a few steps.This combination of robust military architecture, tiny community life and raw Baltic environment makes a visit feel both concentrated and varied. The tower itself is a focal point, but it is also a gateway: after stepping back out into the wind, you are drawn to explore ramparts, old prison buildings, jetties and quiet corners where the long story of this sea fortress continues to unfold.