Mexican experts have discovered that the main pyramid at Mexico's Mayan ruins of Chichén Itzá was at least partially built atop a subterranean river.
Experts from Mexico's National Autonomous University say they found a subterranean cavity about 20 meters deep below the pyramid of Kukulkán, also known as El Castillo.
Geophysics expert René Chávez said Thursday the underground river chamber is naturally covered by rock.
Such underground rivers often connect the open "cenotes," or sinkhole lakes, that dot Mexico's Yucatán peninsula.
The discovery was made using a kind electrical resistance survey, not by excavating.
Archaeologist Guillermo de Anda said the discovery was important. He said it may confirm that the Mayas included symbolic maps of their cosmology in their temples and sacred sites.
