Researchers using an aerial mapping technique known as LiDAR have found previously undetected Mayan defense works, irrigation channels and the remains of tens of thousands of structures in the dense woodlands and jungles of Guatemala's Peten region.

The images revealed industrial-sized agricultural fields, including ones that measured about 12.5 miles (20 kilometers) long.

The mapping technique bounces pulsed laser light off the ground, revealing contours hidden by dense foliage.

About 60,000 individual structures, including four major Maya ceremonial centers, were discovered.

In one of Guatemala's best-explored ruins, Tikal, the images were able to reveal a 90-foot tall pyramid that was previously thought to be a hill.

The discoveries were announced Thursday by an alliance of U.S., European and Guatemalan archaeologists working with Guatemala's Mayan Heritage and Nature Foundation.