For centuries, the dense jungles of Mexico’s Campeche state hid one of the Maya civilization’s best-kept secrets. Beneath layers of tropical forest, an ancient city sprawled — its plazas, pyramids, and causeways buried, forgotten, and left to the mercy of vines, moss, and time itself. For more than a thousand years, this city, now named Valeriana, remained unseen, cloaked by thick foliage that obscured even the tallest of its pyramids.

Then, lasers cut through the forest. Researchers have now exposed Valeriana, which spans seven square miles, featuring pyramidal temples, ceremonial plazas, and a vast network of homes and roads. And it’s all thanks to laser-mapping technology known as lidar.

What LiDAR Can See

Luke Auld-Thomas, a PhD student at Tulane University in the US, found himself contemplating a new approach to one of archaeology’s oldest goals: unearthing secrets of the past that lie just out of sight. He knew that many ancient cities still lingered unseen under Central America’s jungles. And he suspected that the tools to reveal them might already be available.

“For the longest time, our sample of the Maya civilization was a couple of hundred square kilometers total,” said Auld-Thomas. “That sample was hard won by archaeologists who painstakingly walked over every square meter, hacking away at the vegetation with machetes, to see if they were standing on a pile of rocks that might have been someone’s home 1,500 years ago.”

This time, the revelation didn’t come from a blade but from beams of light. In 2013, an environmental project commissioned a laser-mapping survey to monitor forest density, carbon storage, and conservation. Called Light Detection and Ranging (LiDAR/lidar), the technology shoots pulsed lasers from aircraft, bouncing off the forest canopy and ground to create intricate 3D maps.

Originally used to study clouds (and now heavily used in autonomous cars), lidar’s archaeological applications have made waves in recent years, providing a way to uncover what machetes cannot reach. In another stunning discovery made by lidar this year, archaeologists uncovered a huge settlement in the Upano Valley, in Amazonia.

A Mayan metropolis discovered by accident

What’s particularly shocking is the discovery of Valeriana happened “by accident”.

“I was on something like page 16 of Google search and found a laser survey done by a Mexican organization for environmental monitoring,” Auld-Thomas told the BBC.

Auld-Thomas saw an opportunity and decided to take a shot. He and his colleagues from Tulane University and Mexico’s National Institute of Anthropology and History re-processed the 2013 lidar data from a dense swath of Campeche. And there it was, Valeriana, waiting for someone to take notice.

The city had once been a political and ceremonial hub, its structures rising just under a layer of foliage. The ancient site has been named after a nearby lagoon and is believed to be second in density only to Calakmul, thought to be the largest Maya site in ancient Latin America.

Rediscovering Valeriana

Valeriana isn’t just a small settlement or rural outpost; it’s a classic Maya political capital, complete with all the hallmarks of grand urban life. Spread over at least seven square miles, the city contains a network of causeways, temple pyramids, plazas, and a massive reservoir built by damming an arroyo, a seasonal watercourse. In fact, the city even has an “E-Group,” a unique architectural feature the Maya associated with ceremonial events, which could indicate a founding date before 150 A.D.

From the air, the lidar scan revealed structures like an X-ray reveals a skeleton: bones of a city stretching across the land.

“We didn’t just find rural areas and smaller settlements,” Auld-Thomas told The Guardian. “We also found a large city with pyramids right next to the area’s only highway…The government never knew about it, the scientific community never knew about it. That really puts an exclamation point behind the statement that no, we have not found everything, and yes, there’s a lot more to be discovered.”

Indeed, Valeriana is only part of the story. Researchers identified over 6,700 pre-Hispanic structures across 47 square miles, revealing a region so densely populated that it challenges assumptions about Maya civilization’s rural character. With settlement densities at 55 structures per square kilometer, this area of Campeche rivals other densely packed Maya sites in Guatemala and Belize.

New Views of the Maya

Discoveries like Valeriana add fresh layers to our understanding of the Maya, showing a civilization capable of large-scale urban planning and intensive agriculture. Terraces, walls, and water-management structures supported thousands of inhabitants and crops. It’s a vision of the past that calls to mind today’s complex urban landscapes.

As the research team pieced together Valeriana’s ancient neighborhoods and causeways, they found new clues about what life might have looked like during the Maya’s golden age. Scholars used to imagine the Maya largely lived in isolated, rural communities. Yet cities like Valeriana suggest something else entirely — dense, interconnected hubs with sophisticated water and agricultural systems designed to sustain relatively large populations for those times. Perhaps as many as 50,000 people lived in Valeriana during its heyday.

The next step is obvious: it’s time for archaeologists to start digging. Even with lidar, Valeriana’s story is just beginning. Researchers hope to excavate and verify the lidar images, which — while incredibly detailed — cannot provide exact dates or structural purposes. Some structures may not have been homes but served other roles, potentially affecting population estimates and the understanding of social structures.

Imagine that the Maya lowlands may still hide hundreds of sites. And for researchers like Auld-Thomas, Valeriana is just one city in a landscape waiting to be unearthed. It’s a keen reminder of how much remains beneath the surface.