What's hidden inside the ancient Maya pyramids?

The ancient Maya constructed hundreds of pyramids throughout Mesoamerica, from about 1000 B.C. to A.D. 1500, placing a wide variety of artifacts inside of them. 

But what exactly did they put inside of them?

It turns out that, like the pyramids of ancient Egypt, those built by the Maya contained rich treasures and burials. But they also often contained something weirder — smaller pyramids inside the larger ones, experts told Live Science.

Related: What did ancient Egypt's pharaohs stash inside the pyramids?

For example, the pyramid of "El Castillo," at the site of Chichén Itzá in the Yucatán Peninsula, contains a pyramid within a pyramid within a pyramid, like a Russian nesting doll.  

"The ancient inhabitants of the Yucatán Peninsula, when they arrived at a previously inhabited and abandoned site, did not destroy the old structures," Andrés Tejero-Andrade, a professor at the National Autonomous University of Mexico (UNAM) who has studied and written about El Castillo, told Live Science in an email. "Rather a new one was built on top of those already present, and so on," he said, noting that this is why El Castillo has this nesting doll structure.

This practice was not unique to El Castillo; other Maya and non-Maya pyramids have this arrangement, Denisse Lorenia Argote Espino, a researcher at Mexico's National Institute of Anthropology and History (INAH), told Live Science in an email.