Climbing the Burj Khalifa
I can't imagine stepping over the guard rail. Many years ago, on a lark I went on a dual hang glider while in Rio de Janeiro. I spent the first 5 or 10 minutes of my flight repeating, "Holy $#!~" and being absolutely still, lest we fall out of the sky. I finally settled in and enjoyed it. Nowadays, I get antsy just driving on the ridiculously large overpasses they build in Houston.