The Great Wall of China
The Great wall of China is a long very long defense barrier built over 2000 years. It was built because in 8th century BC, China's seven kingdoms were at war, and they needed to defend their kingdoms. But, the Qin kingdom wins, and they conquered china and made it into a empire.
The emperor, Qin Shi Huang, orders them to build a northern wall to defend themselves against the mongols. The length of it was 3100 miles, and the construction time was about 10 years. There was more than 1 million workers that died, and most were buried within the wall. They built watch towers built that were 30 to 40 feet high, with miles of wall linking them together. The watch towers helped a lot with the military communication, and they used smoke signals and lanterns.
But regardless, the wall failed to keep everything out, and Genghis Khan conquered and invaded china in 1211 AD. Then, in 1368 they forced out the mongols and the ming dynasty started. They then built better walls, instead of dirt, stones, and mud, they started using materials like granite, limestone, and brick. This new wall was now 5500 miles long, which is how long it is today. Nowadays, many parts of the wall are deteriorated and broken apart. But that more recent addition has stayed together the best.
"Great Wall of China." History.com. A&E Television Networks. Web. 12 Feb. 2016. <http://www.history.com/topics/great-wall-of-china>.
Great Wall on Mountain. Digital image. Web. 12 Feb. 2016. <https://upload.wikimedia.org/wikipedia/commons/2/23/The_Great_Wall_of_China_at_Jinshanling-edit.jpg>.
Old Great Wall. Digital image. Web. 12 Feb. 2016. <http://blog.hereisbeijing.com/wp-content/uploads/2012/02/old-photo-of-great-wall.jpg>.
Wall Today. Digital image. Web. 12 Feb. 2016. <http://www.solotravel.org/wp-content/uploads/2014/04/great-wall.jpg>.