The moat around the Forbidden City is a rectangle measuring over 2.3 miles long and 20 feet deep. Protecting the four corners are towers called Jiao lou. This is the Southwest Corner Tower on your approach to Meridian Gate. The original wooden defenses were constructed within three months during 1420. The intricate, 72 ridge roofline is patterned after the Pavilion of Prince Teng, constructed in Nanchang, China in 653 AD. Tengwang Pavilion is one of the Three Great Towers of southern China.