Often overshadowed by the Great Wall of China, the Great Wall of Gorgan in modern-day Iran is one of the most sophisticated defensive structures of antiquity. Built by the Sassanid Persians to keep out the Hephthalite Huns, it stretches 195 kilometers (121 miles) and is made of tens of millions of distinct red bricks, earning it the nickname 'The Red Snake.' It featured over 30 forts and a sophisticated canal system that served as both a water supply and a defensive moat. The level of organization required to produce and transport the bricks—estimated at 200 million—showcases the immense industrial capacity of the Sassanid Empire. It is the longest defensive wall in Western Asia and was built centuries before many of the surviving sections of the Great Wall of China.