ancient istambul walls on the bosphorus side

ancient antique architectural architecture attacks bosphorus bosphourus bosporus building byzantine castle citadel city cityscape constantinople construction crusades defend defensive empire europe exterior fort fortification fortified fortress heritage historic historical history istambul istanbul landmark landscape old ottoman outdoor protection ruins sea side sky stone structure summer time tourism tourist tower travel turkey turkish urban used view wall walls water medieval cruzades waterfront islam muslim town defense trip vacation place location attraction east hill turk