The Great Wall of China

The Great Wall of China is the most enormous engineering and building project carried out by humans, especially for its time. From the Bo Hai gulf, off the Yellow Sea in the east, to an area deep in the Gansu province to the west, the Great Wall stretches over 1,500 miles (2, 400 kilometers).
 The Great Wall of China made the country of China itself into a fortress. It is built out of a simple structure of bricks, stone, and dirt. Slabs of stone were used for the base and sides of the wall, and it is filled in with dirt, rocks, and rubble. It ranges in height from 15 to 30 feet (5 to 9 meters), with watch towers rising at regular intervals above it. Visitors can travel the 13 foot (4 meter) wide roadway on the top of the wall.