Pretty scary. I was puckered up.
I used to work ironwork when I was young and crazy. But the highest I ever walked around on a steel I beam was 60 feet. I also climbed up derricks in the oilfield. After the first 90 feet you had to get off the belt and free climb up the rest of the way to the crown....about another 110 feet.
If you were offshore, the drill floor was on the deck of the platform--so that may have been 100 feet above the surface of the ocean. So, if I climbed up the derrick, I would have been about 300 feet above the water. That was pretty exciting.