Really makes one wonder just how old that site is...that age is. It's evident that there was a very ancient civilization which wasn't lost...was destroyed. Some were abandoned but some came to a violent end. Did they come to an end at the same time or in different ages?
The picture - 4th up from the bottom...I'd love to see anyone here try to accomplish that with the methods they argue is capable...make sure to videotape it ; )
All the best.