On the surface, the Kukulkan temple that sits among the ruins of Chichen Itza looks nothing like a Russian nesting doll, but it's essentially the pyramid equivalent, scientists say. They'd known for decades that the 100-foot-tall structure in Mexico's Yucatan state sits on top of a smaller, 65-foot-tall pyramid. Now, a new scan reveals that a third pyramid is beneath the second one, reports the BBC. Hence the Russian nesting doll comparison: "Under the large one we get another and another," says project head Rene Chavez Seguro. The outer pyramid was built between 700 and 1,000 years ago and draws 1 million visitors a year.
This newly discovered pyramid, reaching 33 feet tall, may be up to 1,500 years old and appears to have a staircase and an altar at its peak. It's also slightly out of alignment with the other two pyramids, which "may indicate that there are other buildings hidden at the same level," reports Deutsche Welle. As for why the Mayans built over it, the BBC cites two possibilities: a transfer of leadership or because it was simply in bad shape. CBS News reports the discovery was made using a non-invasive electrical imaging technique called 3D Electrical Tomography, and says no excavation plans have been announced. (This Mexican "mountain" is actually a stack of six pyramids or more.)