Copenhagen - Denmark

"Copenhagen Citadel, once an important fortress to protect the Copenhagen citizens from attack, was used to take evening walks. 

King Frederik VII in the mid-19th century was particularly fond of walking the walls with his commoner wife, Countess Danner, and the tradition of walking the walls on Storbededag is said to be his invention - to show himself to the common Danish crowd." - in: http://english.saxo.ku.dk/calendar/citadel_walk/. Card sent by Dorthe.