The New York Times reports that radar imaging survey techniques have allowed archaeologists to explore the jungle around Angkor in Cambodia and discover remnants of previously unknown temples that may be evidence of an earlier culture that occupied the famous site. The city of Angkor was founded in the ninth century as the capital of the Khmer empire and contained over 1,000 temples covering 100 square miles. The survey around Angkor was carried out in December 1996 by a team from the Jet Propulsion Laboratory in Pasadena, California—a branch of NASA. By transmitting microwaves to the ground and registering signals that are reflected back, the radar produces images of the shape and nature of buried structures. The system has been refined to penetrate the foliage of the dense Cambodian forests. Radar exploration by aircraft or spacecraft has previously been used to chart the course of the Nile river in antiquity and to discover ruins along the Silk Route in China.