The Great Wall of China is, without doubt, one of the greatest engineering feats of the ancient world. According to urban legend, it is the only manmade structure that is visible from the moon. This is, however, not true.
The wall was built over hundreds of years and expended the blood and sweat of hundreds of thousands of people as they sought to protect the northern border of their country from marauding hordes.
The wall is 5,500 miles long although the official length is 13,170 miles. As it crosses hill and dale, it trails up mountainsides at breathtaking angles. The wall was built over the course of 2,000 years under the curatorship of various governments.
Surprisingly, the wall is not continuous. There are parallel walls and circular walls and, in some places, no wall at all. Some of the bricks in the wall have even been bound together with glutinous rice flour. This is one of the first composite mortar samples in the world and is considered one of the greatest inventions of the Ming dynasty because it holds so well it can amazingly survive poor weather and earthquakes.
Unfortunately, the wall is also sometimes called the longest cemetery on Earth. Hundreds of thousands of people died while building it with many of the dead left buried in the wall.