The ancient Maya once believed that Mexico's jungle sinkholes containing crystalline waters were the gateway to the underworld and the lair of a surly rain god who had to be appeased with human sacrifices.
Now, the "cenotes," deep sinkholes in limestone that have pools at the bottom, are yielding scientific discoveries including possible life-saving cancer treatments.
Divers are dipping into the cenotes, which stud the Yucatan peninsula, to explore a vast underground river system.
Not much archaeology in there, it mostly just talks about the underground cave system, its biota (in not much detail), and the possibility of pollution. Actually, not much on the whole cancer-fighting treatments either.