What is the longest structure ever built?

A lot of long bridges and tunnels have been built in recent years, but the longest structure ever built by human beings is over 2,000 years old — it’s the Great Wall of China! Construction on this wall started in the 7th century B.C., and different Chinese rulers added and restored it up until the 17th century A.D. The Great Wall stretches across the mountains of northern China and winds northwest of the country’s capital city, Beijing. In total, the wall is about 4,000 miles long.