CNN Anderson Cooper 360 August 14, 2013 02:53:00
>> reporter: most striking for me is how appearances are so misleading. the cavern is even bigger below the water line, with passageways carved deep into the darkness. but most disturbing could be the view from up top. the round opening is deceptively small. little indication of the cavern that's just beneath my feet. until a hole like this opens up, there's really no warning, is there? >> correct. it is that random and that sudden. and it could happen obviously overnight or at any time. >> reporter: it can, and it does. with thousands of sync sinkholes opening up every year. >> incredible to ...
Source: archive.org