* ARCHAEOLOGISTS DISCOVERED THE Maya city of Caracol, hidden in the jungles of Belize, in the 1930s. In the 1980s, the husband-and-wife team of Arlen and Diane Chase began the daunting project of mapping Caracol and its environs. With teams of assistants and students, they tramped through the rain forest, recording and measuring every archaeological feature they could find. By 2009, after 25 years of labor, they had some of the most detailed maps ever made of a Maya city.
Then they tried a new mapping tool: "light detection and ranging" technology, or lidar. Although lidar had been used for years to survey large-scale features for projects such as urban planning and planetary exploration, only recently had it gained the resolution necessary for archaeological mapping. The Chases joined forces with NASA and the National Center for Airborne Laser Mapping at the University of Houston, which supplied a plane retrofitted to carry a million-dollar lidar machine that flew five missions over Caracol and its environs, mapping the ground with lasers.
When the images came back, the Chases were stunned. The lidar maps showed that in the quarter-century they had spent roaming the rain-forest floor, they had found only about 10 percent of what was actually there. The new maps revealed tens of thousands of previously unknown features, large and small--structures, houses, roads, reservoirs, terracing, sinkholes, caves (some with burials and artifacts), and even open and looted tombs. In a little more than nine hours, the lidar mission had revealed that Caracol was a far larger area than previously imagined, an urban landscape covering 200 square kilometers.
The Chases declared lidar the greatest archaeological advance since carbon-14 dating, which won its discoverer a Nobel Prize and transformed the science of archaeology. It's true that archaeology is on the verge of another revolution because of lidar. The technology will soon strip away the world's jungles to reveal their lost civilizations and hidden treasures, a prospect recently demonstrated in dramatic fashion by Bill Benenson and Steve Elkins.
A few years ago, the two filmmakers had the crazy idea of mapping a large swath of unknown rain forest in the rugged interior mountains of Mosquitia, a region in Honduras. These mountains have the distinction of being among the last archaeologically unexplored regions on Earth, cut off by dense jungles, malarial swamps, roaring torrents, steep ravines, deadly snakes, and the even more formidable Honduran bureaucracy.
Benenson and Elkins were looking for a legendary lost city, known as La Ciudad Blanca (the White City), long rumored to be hidden in the area. They persuaded the National Center for Airborne Laser Mapping to undertake the speculative project, the first to use lidar for pure exploration. (Previously, it had only been used to survey known sites.) And in May 2012, they spent a number of days flying over the Mosquitia mountains, logging a little more than eight hours of actual mapping time.
I accompanied Benenson, Elkins, and their team to Honduras as a journalist--a trip I later wrote about for the New Yorker--even though I believed their chances of finding something were small. Nothing much happened in the first few days, as the plane gathered raw data. But on the morning of the fourth day, the chief mapping engineer had crunched enough data to create maps of an isolated valley in the targeted area. Previously a skeptic, he burst out of his bungalow, running like a madman, waving his arms and yelling, "There's something in the valley!"
When we crowded into his room, we could see that the maps were covered with blurry, unnatural features that even to our inexpert eyes looked like ruins. Later analysis by archaeologists specializing in Mesoamerica revealed two, possibly three, unknown cities in those images, encompassing pyramids, plazas, roads, canals, terracing, rectangular mounds, and walls. …