The Great Wall of China is an ancient wall in China. The wall is made of cement, rocks, bricks, and dirt. It was finished in 1878 and it was meant to protect the north of the empire of China from enemy attacks. It is the longest structure humans have ever built. It is about 21,196 kilometers long, 9.1 metres (30 feet) wide and 15 metres high. The earlier sections on the wall are made of compacted dirt and stone. Later in the Ming Dynasty they used bricks. There are 7,000 watch towers, block houses for soldiers and beacons to send smoke signals.
Nineteen walls have been built that were called the Great Wall of China. The first was built in the 7th century BC. The most famous wall was built between 226–200 BC by the first Emperor of China, Qin Shi Hong (Qin Pronounced as Chin), during the Qin Dynasty. Not much of this wall remains as people have been stealing from it. It was much farther north than the current wall. The current wall was built during the Ming Dynasty. Image by Markus Winkler from Pixabay