The Sasanian Empire (224 CE – 651 CE), which was a contemporary of the Roman and later Byzantine Empires, was once a great power. And like other great powers it built great walls to mark and control its borders. These included the Wall of the Arabs (in the southwest), Walls of Derbent (in the northwest at the Caspian Mountains) and Great Wall of Gorgan (in the northeast). Remains of the Sasanian border walls still exist, particularly in Derbent where they are a UNESCO world heritage site.
