The scariest edge I have been on is in the Taihang Mountains in Central China. We were visiting the Guoliang Tunnel—hand made over 5 years by 13 men to connect the village of Guoliang to the outside world. Prior to this they were living on the edge with only a sky ladder to physically take every thing up. The tunnel itself is described as one of the scariest roads in the world and the video shows why. You can see the edge at every twist and turn.
http://eclecticoddsnsods.com/2015/04/07/eclectic-corner-9-edge/