You should just watch the movie, but it's if the idea that if you let a nuclear meltdown occur, it would melt through the earth, all the way to China. Of course, it could only melt its way to the earth's core.
a) The human threats to the Great Wall of China can include Vandalism on the Great Wall, littering on the Great Wall, Destruction of the Great Wall, carving into the wall, other structures being...