National Geographic : 2015 Oct
lost city 113 Elkins labeled T1, T2, and T3, the T standing for “target.” The first was an unexplored river valley surrounded by ridges, forming a natural bowl. “I just thought,” Elkins said, “that if I were a king, this would be the perfect place to hide my kingdom.” But the images were inconclusive; he would need a better way to peer through the dense jungle canopy. Then, in 2010, Elkins read an article in Ar- chaeology magazine that described how a tech- nique called lidar (short for light detection and ranging) had been used to map the Maya city of Caracol, in Belize. Lidar works by bouncing hundreds of thousands of pulses of infrared laser beams off the rain forest below, record- ing the point location of each reflection. The three-dimensional “point cloud” can be manip- ulated with software to remove the pulses that hit trees and undergrowth, leaving an image composed only of pulses reaching the under- lying terrain—including the outlines of archae- ological features. In just five days of scanning, lidar revealed that Caracol was seven times larger than had been thought from 25 years of on-the-ground surveying. One downside of lidar is its expense. The Caracol survey had been carried out by the National Center for Airborne Laser Mapping (NCALM) at the University of Houston. For NCALM to scan just the 55 square miles of the three valleys would cost a quarter of a million dollars. Fortunately, by this time Elkins’s un- bounded eagerness to find the White City had infected Bill Benenson, another filmmaker, who was so taken with the project that he decided he would finance it himself. The initial results were astonishing. There appeared to be ruins strung along several miles of the T1 valley. (I reported on this initial dis- covery in the New Yorker magazine in 2013.) A site twice the size was evident in T3. Although the larger structures were readily apparent, a finer analysis of the images would require the eye of an archaeologist skilled in the use of lidar. Elkins and Benenson turned to Chris Fisher, a specialist on Mesoamerica at Colorado State University.