"Kastellet", the Citadel, located in the northern part of Copenhagen is one of the best preserved citadels in the world. Kastellet was constructed during 1625-1640 and has been used as defence several times - latest in 1940 during the German invasion of Denmark (World War II). Today Kastellet is open for the public and serves as a recreation area for tourists and citizens. The military use continues and includes housing of the Danish Home Guard, Military Intelligence, Judge Advocate Corps and historical museums.
(Image shot handheld with Sony NEX-7 18-55mm kit lens @ 18mm.)