The fortress was originally named Citadelt Frederikshavn after King Frederik III.
The onsite Kastellet Mølle windmill replaced a previous 1703 version that burned down in 1847.
The grounds host a small prison, the 'Slibestenen,' which held historical figures including Johann Friedrich Struensee.
Kastellet is home to the last remaining windmill within the Copenhagen city center.
The pentagonal shape was a classic Dutch military fortification design chosen for its superior defensive angles.
Kastellet is one of Northern Europe's best-preserved star fortresses, founded in 1626 by King Christian IV. It features a distinct pentagonal design surrounded by a moat and earthworks, originally built to protect Copenhagen's harbor. The fortress remains an active military site under the Danish Ministry of Defence. Within the ramparts, you will find the 18th-century St. Alban’s Church, a windmill dating back to 1847, and the Gefion Fountain located just outside the perimeter. The ramparts are topped with walking paths that provide elevated views of the city's harbor entrance. The site serves as both a historical monument and a public park frequently used by local joggers. Buildings inside the complex are primarily occupied by military personnel and are not accessible to the public. The layout includes five bastions named King's, Queen's, Count's, Princess's, and Prince's.
The elevated path near the windmill provides an unobstructed view of the red-painted barracks and the moat.
Walk the entire perimeter on the upper grass-covered ramparts for the best vantage points.
Visit during the early morning to avoid crowds and observe the military personnel beginning their day.
Combine your visit with the nearby Langelinie promenade to see the Little Mermaid statue.
Do not attempt to enter the fenced-off military office buildings or restricted administrative zones.
The outdoor grounds are accessible throughout the year, but specific internal buildings are closed to the public.
Respect the restricted areas marked for military use only; stay on public pathways.
