Wed, Jun 9, 2010
the peninsula of Yucatan have an amazing complex of underground rivers. this is unique on Earth, and it's what sustained their rain-forests for millenia. there are several "holes" like this one, and the Mayans called they the "entrances" to the underworld - they believed that, when you die, you had to travel your way through these caves to Xibalba.
there's a great documentary about the first divers who dared to explore those underground rivers, as they try to map and understand it. I really recommend watching it in hi-resolution (the images are breath-taking), but if you want to take a look, it's available on youtube...
on this documentary, the divers alert about the dangers of building a city above these underground rivers, both to secure human lives and to preserve this wonder of nature. too bad people don't listen...