Kastellet was designed concerning 1662 and 1725 and was a cornerstone of King Christian IV’s defenses of Copenhagen. It continues to be in use by the military and inside there are extensive, pink brick, slate-roofed structures, a parade floor, and in some cases a Dutch-type windmill. A check out to https://econopass.com/travel/10-must-see-and-do-in-copenhagen/