Kastellet was created between 1662 and 1725 and was a cornerstone of King Christian IV’s defenses of Copenhagen. It continues to be in use by the army and inside of there are actually extended, pink brick, slate-roofed properties, a parade ground, and in many cases a Dutch-design and style windmill. https://allyourbookmarks.com/story17186722/little-known-facts-about-copenhagen-things-to-see