Don, there you have the basis for more than one science fiction novel or film.

From the Smithsonian, This Ancient Maya City Was Hidden in the Jungle for More Than 1,000 Years
Archaeologists surveying the ruins of Ocomtún found pyramids, stone columns and a ballgame court

Researchers from Mexico’s National Institute of Anthropology and History (INAH) have discovered the remains of a centuries-old Maya city in the Balamkú ecological reserve on the Yucatán Peninsula.

In a statement, lead archaeologist Ivan Šprajc says the settlement probably served as an important regional center during the Maya Classic period, which spanned 250 to 1000 C.E. The team named the newly discovered ruins Ocomtún—“stone column” in Yucatec Mayan—in honor of the many columns found at the site.

“The biggest surprise turned out to be the site located on a ‘peninsula’ of high ground, surrounded by extensive wetlands,” says Šprajc in the statement, per Google Translate. “Its monumental nucleus covers more than [123 acres] and has various large buildings, including several pyramidal structures [nearly 50 feet] high.”

There are lots of links to things mentioned in the topic, and a nice photo of the LIDAR view of the location. (Ever since I learned about LIDAR at a conference in ~ 1999, I figured it was going to appear again and again in reports about the discovery of this kind of archaeological site.)