What could possibly motivate a civilization to build a wall with such scale and breadth? Fear.
After the unification of smaller states into one country in 220 BC, the the first emperor of Qin Dynasty, Qin Shi Huang, organized the northern states into constructing the Great Wall to protect from various nomadic armies. The wall winds and meanders through a staggering 5,500 miles of the Chinese landscape. The small portion that I climbed was about 2 miles in length and took me over 4hours to climb. There wall is extremely steep and dangerous to climb at certain areas, but after reaching one of the watchtowers near the highest point of the wall, it was well worth it.