More than half a millennium after the collapse of the Mayan civilization, the members of a neighboring Central American society suddenly gathered their most sacred belongings, buried them in the center of town, and vanished.

"There's a big question about who these people were," the best-selling author Douglas Preston, who visited the remnants of this city, told Business Insider. "What happened to this civilization? Why did they abandon this city so suddenly?"

Preston was part of a research mission launched two years ago to explore the ruins of what is said to be a lost civilization. He wrote about his recent trip through the Honduran jungle in the new book "The Lost City of the Monkey God: A True Story."

Some have said that the buried remnants correspond with an ancient, legendary "White City" — a town of extreme wealth that vanished some 600 years ago. Since the 1900s, rumors of this forgotten city had danced on the lips of explorers, aviators, and tourists excited by the prospect of uncovering hidden treasure. But no one knew much about the people who once lived there.

Even after some parts of an abandoned village, including remnants of plazas and pyramids, were uncovered in 2012, during the first expedition to the area, anthropologists and archaeologists remained stumped.

"In the words of the leading Honduran archaeologist on our expedition, 'What we know about this culture is ... nothing,'" said Preston.

Nevertheless, some intriguing theories have emerged. Researchers on the most recent trip found a cache of nearly 500 intricately carved stone objects inside something Preston described as "a grave not for a person, but for a civilization."

The legend of the 'lost city' and the discovery that made archaeologists fume

The 1,000-year-old ruins — whose timeline coincides with the "White City" — were buried in the rainforest, in a round valley ringed by steep cliffs. Since a team of researchers uncovered them in 2012, they've been revisited by more research teams, including Preston's.

View photos lost city archaeology honduras national geographic white city monkey god More

When news outlets picked up the story, most portrayed it as an ancient mystery that had finally been solved. National Geographic ran with the headline "Exclusive: Lost City Discovered in the Honduran Rain Forest." NPR announced "Explorers Discover Ancient Lost City in Honduran Jungle."

Related Video: Legendary 'Lost City' Unearthed in the Honduran Jungle (2016)

For more news videos visit Yahoo View, available now on iOS and Android.

There was one problem, though, according to researchers who signed a public letter condemning the claims in the news: The ruins were not the "lost city" of lore — and worse, they may not have been lost to begin with.

The dissenting researchers — including Chris Begley, an archaeologist at Transylvania University who has 20 years of experience in the region — said the National Geographic story exaggerated the findings and ignored the region's indigenous people. National Geographic responded to the letter by linking to a statement from the research team that says its story never claimed to have discovered the "lost city," but merely a lost city in the region.

The people who disappeared

Controversy notwithstanding, the teams of researchers and documentarians who visited the site in 2012 and 2015 came away riveted by what they'd seen. Preston and several other archaeologists maintain that they set foot on terrain that had been untouched for half a millennium. And they say the clues these people left behind point to a tragic end.

"It's hard to believe that in the 21st century a lost city could still be discovered, but that's exactly what happened," he said. "People hadn't touched foot there in 500 years. It's absolutely true."