Mexican experts have discovered that the main pyramid at Mexico's Mayan ruins of Chichen Itza 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 (yards) deep below the pyramid of Kukulkan, also known as El Castillo.
Geophysics expert Rene Chavez 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 Yucatan peninsula.
The discovery was made using a kind electrical resistance survey, not by excavating. Chavez said . . .
