Why would an ancient civilization -- often advanced for it's time -- suddenly cease to exist? The only things left: it's artifacts and abandoned architecture. Conspiracy theorists would have their say, everything from alien abduction to time travel. But in truth, the reasons are far more mundane: natural disasters, climate change, invasions and economic upheaval.

Here are 12 fascinating civilizations that vanished... and we don't know why.

-Jon
posted by Jon at 10:37 PM  I   I  0 comments