Great Wall of China

Built on an east-to-west line across the northern borders of China to protect from invasion. Made from stone, brick, wood and tamped-down earth, the wall was commenced in the 7th century with many additions throughout the subsequent years. Said to be the longest man-made structure in the world, it is now a UNESCO World Heritage Site. The main wall is nearly 3,460 km long. It is said that it cost the lives of more than one million people in the making, giving it the name "the longest cemetery on earth".