Subterranean river discovered beneath Mexico's Chichen Itza ruins

1	Experts have discovered that the main pyramid at Mexico's Mayan ruins of Chichen Itza was at least partially built atop a subterranean river.
2	Mexico's National Autonomous University scientists say they found a subterranean cavity about 20 metres deep below the pyramid of Kukulkan, also known as El Castillo.
3	Geophysics expert Rene Chavez said on Thursday that the underground river chamber is naturally covered by rock.
4	Such underground rivers often connect the open cenotes, or sinkhole lakes, that dot Mexico's Yucatan peninsula.
5	The discovery was made using a kind electrical resistance survey, not by excavating.
6	Chavez said one corner of the pyramid rested on the underground chamber, so it was in danger of collapsing.
7	Archaeologist Guillermo de Anda said the discovery was important.
8	De Anda, who did not participate in the study, said it may confirm that the Mayas included symbolic maps of their cosmology in their temples and sacred sites.
9	The cenotes that surround the pyramid could represent the four points of the compass.
10	The river at the center might represent the center of the Maya's universe, which they thought of as a tree with roots reaching below ground.