Most of these structures were astronomical observatories as much as anything. Kind of hard to explain, but see the protrusions? On June 21, the beginning of Winter Soltice here, the shadows from one of the protrusions points directly to the other protrusion. Only day of the year it happens. You find this in many places in these structures. They knew what they were doing.

The second picture is a group of kids, walking along, joking, pushing and shoving, like kids. But notice how close they are to the edge and paying no attention to it at all. It is at least a 500 to 1000 foot drop straight down.