Walls are as old as humans, and often are built to keep others out and offer protection. They also are used to keep people contained in one area, and they can be extremely divisive. The Great Wall of China, the Berlin Wall and myriad border walls can be found across the world and within all countries. But walls also can fall or be torn down. Such barriers, though, are cropping up a faster rate again across the globe, and even more are planned.