By: Ginger Perales

Researchers working at Chichen Itza, the Maya archeological compound in the Mexican state of Yucatan, have discovered a third structure hidden within the Kukulkan pyramid, also known as El Castillo (The Castle). This recently discovered structure, a 10-meter-tall pyramid, was found inside a 20-meter-tall pyramid which itself was found enveloped by the 30-meter-tall visible structure.

“It’s like a Russian nesting doll. Under the large one we get another and another,” geophysics expert René Chávez Seguro, who led the project, says in the Guardian.

The presence of the third structure suggests the Kukulkan pyramid was built in three separate stages. The first, innermost pyramid was constructed between the years 550 and 800. The middle pyramid, which was discovered in the 1930s, was built between the years 800 and 1000. The largest, final pyramid dates back to the years 1,050 to 1,300.

Structures like El Castillo were constructed one on top of the other for a variety of reasons, including the arrival of new leaders or deterioration. The research team is hopeful the find will reveal information about the original Maya culture prior to influences from central Mexico populations. The Mesoamerican Maya civilization was notable for its hieroglyphic script, the only fully developed writing system within the pre-Columbian Americas, and also for its architecture, art, calendar, mathematics, and astronomy system.

In 2015 archeologists discovered the pyramid was built on top of a cenote (sinkhole), common to the region and considered sacred by the Maya. The sinkhole under the temple is approximately 82 by 114 feet (25 by 35 meters) and could be up to 65 feet (20 meters) deep. Researchers also found that the pyramid sits on a 16 foot (4.9 meter) layer of limestone on top of the cenote.

The discovery of the limestone layer, like the discovery of the third pyramid, was made using a new noninvasive technology involving the placement of electrodes in the area surrounding a structure and sending an electrical current into the ground. While the current is being emitted measurements to determine whether or not sub-surface elements are impeding or increasing the electrical potential are taken and then processed with software that creates three-dimensional maps of the subsurface area.

A Mesoamerican step-pyramid, El Castillo dominates the center of the Chichen Itza complex. It was built by a pre-Columbian Maya civilization between the ninth and twelfth centuries CE. The pyramid functioned as a temple to the Yucatec Maya Feathered Serpent god Kukulkan, who was closely related to the Aztec god Quetzalcoatl.

The National Institute of Anthropology and History has begun closing pyramids and monuments to the public in an effort to preserve the buildings, so while visitors can still walk around them, they can no longer climb or enter them. Climbing El Castillo was halted after a woman fell to her death in 2006. Today, it remains one of Mexico’s most recognized pre-Columbian structures.