There are many contenders for the strongest fortress in history (Malumat in Iran or the island fortifications of Malta to name a few). But nothing can compare to the Theodosian City Walls of Constantinople. Built in 440 AD, they repelled over a dozen invasions, from Atilla the Hun to the Umayyad Caliphate to the Avars to the Russians. And they allowed Constantinople to develop into one of the richest cities of the ancient world.   TO HELP OUT THE SHOW Leave an honest review on iTunes. Your ratings and reviews really help and I read each one. Subscribe on iTunes or Stitcher