Kastellet (The Citadel), Copenhagen

A Star-Shaped Fortress on the Edge of the Harbour

Kastellet, known in English as The Citadel, sits like a green pentagram beside Copenhagen’s harbour, its earth ramparts and wide moat forming one of Northern Europe’s best‑preserved star fortresses. Laid out in the 17th century as part of Copenhagen’s defensive ring, it was designed so soldiers could survey every approach line, a geometry that is still clearly legible from the paths atop the walls. As you wander the perimeter, the tranquil scene belies its original purpose. Grassy slopes tumble to the water, trees frame views of the harbour, and joggers trace the same lines once patrolled by guards. The fortress still belongs to the Danish armed forces, lending a subtle sense of ceremony and order, yet the grounds function as a relaxed public park where military history and everyday city life intersect.

From Royal Ambition to Modern Military Role

The story of Kastellet begins in the 1600s, when Danish monarchs reshaped Copenhagen into a fortified capital capable of withstanding European power struggles. Commissioned in the reign of King Frederick III and initiated under King Christian IV, the citadel was built to a cutting‑edge star design, enabling overlapping fields of fire and stronger bastions than medieval walls could offer. Over the centuries, the fortress witnessed sieges, shifting borders and evolving warfare. In the 19th century it served primarily as barracks and logistical hub; during the Second World War it was occupied by German forces, a reminder that even this peaceful corner of the city once sat at the fault line of European conflict. Today, parts of Kastellet still house military institutions, but the emphasis has shifted from defence to remembrance and quiet reflection.

Windmill, Chapel and Colour-Washed Barracks

Inside the walls, Kastellet feels like a self‑contained village. Rows of vividly painted red barrack blocks line the central axis, their orderly facades and white‑framed windows creating a striking contrast with the green embankments around them. These 18th‑century buildings once housed soldiers and officers and now provide a rare glimpse of historical military architecture in daily use. Close by, the baroque Citadel Church stands with understated elegance, its pale exterior and simple interior occasionally hosting services and concerts. On one of the bastions, a traditional windmill from the 1840s recalls the days when grain was ground here for the garrison, its sails framing views over the harbour. Together, these features give the fortress an almost pastoral character, more village green than garrison, especially on calm days.

Walking the Ramparts and Exploring the Bastions

For many visitors, the highlight of Kastellet is the chance to walk the full loop of its ramparts. The path undulates gently along the five bastions, revealing new perspectives at every turn: glimpses of the Little Mermaid and the open sea, the domes and spires of central Copenhagen, and the straight lines of the barracks town below. It is an easy, accessible walk that nonetheless conveys the scale and ingenuity of the original fortifications. Down at moat level, tree‑lined paths follow the water’s edge, popular with runners, dog‑walkers and families. Benches invite you to pause and watch waterfowl on the moat or study the subtle angles of the defences. In several spots, sculptural monuments and memorials commemorate Denmark’s international missions and military history, adding a contemplative dimension to a casual stroll.

A Green Refuge in the City

Despite its martial origins, Kastellet today feels primarily like a green haven. In spring, the lawns and ramparts burst into fresh colour; in summer, the long Nordic evenings make it a pleasant place for unhurried walks; autumn brings warm tones to the trees; winter can cloak the bastions in frost, sharpening the fortress outlines. Throughout the year, the atmosphere is notably calm compared with busier central parks. Its location near major sights such as the Little Mermaid, St Alban’s Church and the harbourfront makes Kastellet easy to weave into a wider day out, yet it retains a self‑contained serenity. Whether you come for military history, architectural geometry or just a quiet circuit in the fresh air, the citadel offers an unusually layered urban landscape: part monument, part park, and part living military site.