10The Great Wall of China, China
While not a traditional fortress in the classical sense, the Great Wall of China is one of the most formidable and impressive defensive structures ever built. Spanning over 13,000 miles, it was constructed over several dynasties, beginning as early as the 7th century BC. The wall was designed to protect China from invasions by nomadic tribes and later from the Mongols. Along its length are numerous watchtowers and fortified gates, making it a massive defensive system. Its scale, historical significance, and the sheer effort that went into its construction make the Great Wall one of the most awe-inspiring fortifications in the world.
