Located in northeastern China, the Great Wall stretches approximately 1,500 miles (2,400 kilometers). It averages 25 feet (7.6 meters) tall, is 15 to 30 feet (4.6 to 9.2 meters) wide at the base, and 10 to 15 feet (3 to 4.6 meters) wide at the top. The wall was originally erected to keep northern invaders out of China. Though part of the Wall was initially built in the third century B.C.E., the wall was expanded over the course of succeeding centuries.