The Yedikule Citadel http://bit.ly/7kule-citadel
The Yedikule Citadel (The Castle of The Seven Towers)
Yedikule is an interesting structure, partly By-zantine and partly Ottoman. The walls form a five-sided enclosure, which surrounds a big courtyard with the remains of a minaret in the centre.
http://istanbul.hasanyildiz.com
https://fb.com/historicalistanbul/