Barbican in Warsaw, Poland
Nope, not quite a castle. This fortified structure is the Barbican, originally built in 1540 in between the Old and New cities by Jan Baptist the Venetian, an Italian expat living in Poland. Of course, no sooner had the workers finished their project than this type of fortified barbican became archaic in light of the recent invention and explosion of artillery weapon usage. (Only once was it used to defend the city; in 1656 against the formidable Swedish Army). Almost entirely destroyed during WWII (like roughly 85% of Warsaw), it was later rebuilt by the Polish government based on 17th century etchings under the theory that it would bring in tourism dollars. Today, it still serves little purpose other than making a dramatic way of walking down ul. Nowomiejska in the middle of the old (although it’s rebuilt, so actually quite new) centre of Warsaw.