castles

What if the Byzantines, influenced by Western Europeans during the high middle ages started building Castles to fortify important positions? How would this affect the Empire's development and territorial integrity? Could this help secure Anatolia from Turkish raiders, and possibly help them...

Are there any cities that fell out of prominence in ancient times, but definitely could have retained prominence into the modern era? Or locations that didn't host strategic or capital cities historically, which definitely could have? For example: Hattusa (Had 50,000 people in the Bronze Age...