The Pentagon spans a gross area of about 6.34 million square feet (about 34 acres). This building includes five floors plus a basement and a partial mezzanine, reaching a total height of about 71 feet. Within the halls of the Pentagon are five concentric pentagonal rings, intersected by 10 corridors for a total walking distance of about 17.5 miles. Despite the Pentagon's massive size, the average time to walk between two points is only about seven minutes. In the center of the Pentagon is the five acre area known as the Center Courtyard.