Spanning over 6,400 km (or 4,000 miles), the construction of the Great Wall of China began in the 5th Century.  Sections of the wall were originally constructed to protect the northern borders of China from fierce nomadic tribes from Central Asia, known as the Xiongnu.  Centuries later, the Great Wall would continue to protect China from other raiding factions.  Lego builder KK shares images of one Great Wall creation in his Brickshelf folder.