Lidar is best known as the technology that enables self-driving cars to make sense of the world (and lately as the scanning tech that showed up in this year’s iPad Pro refresh). But the tech, which uses pulsed laser light to measure range, is also utilized in other ways — such as helping uncover ancient Mayan relics from the sky.

That’s what researchers at the University of Arizona in Tucson recently managed when they used an airborne lidar system to discover the oldest ceremonial ground in the Maya area in southeast Mexico. This turned out to also be the largest in the entire prehispanic history of the region — about 1.4 kilometers in length and 15 meters in height. Aguada Fénix, as it’s known, was constructed somewhere between 1,000 and 800 BC, according to a Bayesian analysis of radiocarbon dates carried out by researchers on the project. That pre-dates the construction of the Mayan pyramids.

“Lidar emits laser beams from an airplane,” Takeshi Inomata, professor in anthropology at the University of Arizona, told Digital Trends. “Some laser beams penetrate through tree canopies, and reveal the shape of the ground surface. The site was not known because it is so large horizontally that if you walk on it, it just looks like a part of natural landscape. Its rectangular shape became clear with the bird-eye view of lidar.”

As Inomata points out, traditional mapping on the ground level would have taken significantly longer to carry out. Using lidar, however, they were able to create a 3D map of the surface by flying a plane overhead, while scanning the ground below. This helped reveal the enormous size of the site, which reportedly would have taken around 10 to 13 million person-days to construct and likely involved thousands of people moving up to 4.3 million cubic meters of earth.

This is not the first time lidar has played an important role in similar research. In 2016, scientists used airborne lidar to create a map of a long-lost city hidden beneath the jungle in Cambodia. Meanwhile, the Earth Archive — launched by two professors at Colorado State University — is an ambitious project that seeks to use lidar scanning to scan the entire planet to generate maps of cultural, geological, and environmental artifacts at risk in the face of climate change.

A paper describing the recent University of Arizona project was published in the journal Nature.