A lot of the wonders that I’ve mentioned thus far are pretty fanciful in nature. The Great Wall of China is a unique wonder of the world, then, because it has served a key tactical purpose in China for many years. The Great Wall is, well, a wall. It’s primarily built of stone, brick, and wood, and it spans the historic northern borders of the country. The wall has been constructed, improved, and lengthened over many years and across many dynasties. As you can imagine, it would have been impossible for this empire to have constructed a 13,171 mile long wall under a single emperor. Aside from being beautiful, the great wall was also used as a form of border control. It allowed China to protect itself from invasions and raids. Although the myth that the Great Wall of China can be seen from space is untrue, it cannot be denied that this is one of the most historically significant feats that the world has ever seen.