The Great Wall of China is unbelievable. I walked a few miles in an upwards direction with a few friends. We would see a peak in the distance that looked to be higher than all of the rest and so our goal was to get to it. Once there we would see that the next peak was actually higher. This continued until we could no longer walk.
After seeing the wall and the mountains that surround it I have no idea why anyone would want to try to invade another country. I would have stayed home with a nice warm fire.