Archaeologists excavating what they thought was a tomb in northern Guatemala have come to a new conclusion: the site was an ancient steam bath complex used 2,500 years ago. It is an amazing example of advanced Mayan engineering, many centuries before the peak of that civilization. Live Science reports:

“In the Maya beliefs, caves and baths are treated almost the same way: the places where not only the gods, but also the first people were born and emerged from,” Źrałka told Science in Poland. “They are also considered to be entries to the underworld, the world inhabited by gods and ancestors. Caves and steam baths were also associated with the harvest and the place of origin of life-giving water.”

The steam bath certainly looked cave-like when the archeologists first discovered it. First, the team found a downward-sloping tunnel carved into the rock. But this tunnel is actually where the steam bath’s excess water flowed, the archaeologists soon discovered.

The Maya also constructed an easy way to enter the bath; both sides of the tunnel have stairs leading up to the steam room, which has rock-cut benches where the bathers could sit. Across from the entrance is an oval-shaped hearth, where large stones were likely placed, heated up and then splashed with water to produce steam, the archaeologists said.

The steam bath was discovered at Nakum, an important Maya center that peaked about 1,500 years after the baths were constructed. This suggests a surprisingly long period in which Mayan engineering maintained a high level of sophistication. Excavations have revealed many stone temples and palaces, as well as raised causeways to make travel possible during the rainy season.

This discovery comes just a year after a much grander discovery was announced in the Petén region of northern Guatemala. This was an enormous complex of urban centers that housed up to 5 million people, and has since been swallowed by the dense rainforest. The urban agglomeration reached its greatest extent around 800 AD, then completely disappeared by the time the Spanish arrived. These discoveries remind us that most of what we know about pre-Columbian civilization comes from the testimony of conquistadors who encountered them directly; archaeology is just beginning to give us a much fuller picture.