Unlike the church. Located on the way to the Little Mermaid, the star-shaped fortress Castelletry. The interior is Baroque and built in 1704. It was owned by the Danish Ministry of Defence but has been used as a parish church since 1902. On October 28, 1626, King Christian IV ordered the construction of Castellet as a defensive wall in northern Copenhagen. The king had a grand plan to build it into a castle as a refuge. But plans were scaled back for economic reasons. His next king, Frederick III, continued the project. After the Swedish siege of Copenhagen (1658-1660 years), Dutch engineer Henrik Ruth was involved in the reconstruction and expansion of the fortress. The fortress is known as Frederick Castle (Citadellet Frederikshavn), but Castellet is more widely known.