The Great Wall of China is 13,170 miles long. Thanks to the modern measuring techniques, and after an archaeological survey taking more than five years, the total length of the world's largest man-made structure had been finally revealed in 2012, as 13,170.69 miles. The surprising length is more than twice as long as the previous estimates. The Great Wall of China took more than 2,000 years to build. It was built in different areas by different dynasties to protect different territorial borders. The Great Wall, one of the greatest wonders of the world, was listed as a World Heritage by UNESCO in 1987.