Kastellet

Kastellet is a well-preserved 17th-century star-shaped fortress near Copenhagen’s harbor, still used by the Danish military. Visitors can walk the ramparts, see the historic windmill and moat, and explore barracks, bastions, and St. Alban’s Church. It offers calm green spaces with city views, easy access from the Little Mermaid, and insights into Copenhagen’s defenses under King Christian IV and Frederik III. Entry is free, and the grounds are open daily, making it a convenient stop for history, architecture, and leisurely walks without leaving the city center.