A team of archaeologists have discovered a third pyramid inside the Kukulkan pyramid located in the ruins of Chichen Itza in Mexico.

The Mayan pyramid, thought to have been completed between 800 and 1000 A.D., was discovered to have a second pyramid during research in the 1930s but only recently have studies shown there is a third pyramid inside creating a sort of Russian doll effect.

The researchers involved in the study used a 3D scanning method called electrical resistivity tomography to non-invasively look inside of the ancient structure where they made the discovery. The third structure measures at 10 meters tall (33 feet) and nestles inside the second pyramid.

The team believe it could indicate a small entrance to an alter: “The structure that we have found, the new structure, is not completely in the center of the Kukulkan pyramid. It is in the direction where the cenote is,” said Rene Chavez Segura, a scientist at the National Autonomous University of Mexico, or UNAM. “This could either confirm or hypothesize that the Mayans when they built this structure that they knew of the existence of this cenote.”

The discovery has opened the eyes of researchers to fresh clues and information about the Chichen Itza site and there’s hope that more can be understood about the economical and political issues of the era.

“If this could be investigated in the future, this structure would be significant because it would speak to the first few periods of habitation of the site and would provide information about how the settlement developed,” said Denisse Argote from the National Institute of Anthropology and History. “With the discovery of this structure we’re talking about something from the pure Mayans. A lot has been excavated, and there is a lot of information on the transitional periods (of the Mayas) and there is a Mexican style at the site, but there is little information on the original site.”