Took my kids to some cliffs south of Sydney. Very sharp, vertical granite cliffs, but not very high. I tried to crawl to the edge and look over. Had to get right down and crawl towards the edge- I felt such vertigo I felt I could have lost my balance and gone over- and that was lying down! I don't know how rock climbers do it- I just keep away! Never understood how being upside down in an aeroplane can be so easy (particularly if your instrument flying isn't very good!), but 80 feet on a balcony or cliff can freak you. I used to keep so quiet about this until I discovered many other pilots were similar!