Ancient stone walls, built for power and security, vary dramatically in scale. While most served as city or military fortifications, the Great Wall of China dwarfs all others, stretching over 21,000 km." decoding="async" fetchpriority="high">Ancient stone walls, built for power and security, vary dramatically in scale. While most served as city or military fortifications, the Great Wall of China dwarfs all others, stretching over 21,000 km. As we consider the monuments of the past which have become landmarks within our scenery, few pictures come more vividly to mind than those of great stone walls winding their way across the skyline. Such…