I don't know what it is, my stomach just lurches to my toes when I lean over a bridge, when I see someone base jump, bungee jump, or sky dive. But, luckily its not paralyzing. I can usually get on the roller coaster, or get to the top floor of the building just fine.
But this picture just scares me! These were men working on sky scrapers in New York. I don't care what I was being paid, I couldn't do this.