All right... let me chime in here too.
Heights are my kryptonite. My knees buckle and I have severe mental problems when dealing with the heights issue. I even have trouble driving over certain bridges like the Skyway bridge in Tampon. I was in Charleston SC a few weeks ago and I had to pull over and let my wife drive over the new suspension bridge they have there (it's better than the old one that used to be there... but I say fuck both of them).
Anyway, several years ago my wife and I went to Costa Rica for our anniversary. My wife was dead set on doing this zip line that started on the top of a volcano in Arenal that was the world's highest and fastest zip line. She left out the part about it being the world's highest. So I had no idea what I was getting myself into. We were staying on the Pacific coast (Playa Conchal) and hired a driver to take us half way across the country to this fucking volcano. I wasn't going to wimp out despite my extreme fear. If I could tell you this story in person with my wife present... you would really understand the magnitude of the situation. So I fucking toughed it out and went with her.
Here is a video of just one of the stages of this zip line. I can't remember how many of them it takes to get to the bottom of that fucking volcano,,, but it was many. One of them reaches speeds of over 60 mph as I recall in my nightmares.
My wife is smiling and waving right in the front of this vid while standing on the edge of the "death zone". I gave my camera to one of the guides to video so that I could see what I went through later when I got home... that's because I fucking kept my eyes closed the whole time I was going across a line. If you look closely... at 37 seconds in, you can see a guy sitting in the back righthand corner of the platform staring away from the start of the zip line. That guy is me... I couldn't even look at it. The vid will show you just how high up it was. I did wave to him when he started screaming. Which you can see if you look closely... but I never looked.
This was extremely difficult for me to endure. I will NEVER go on another one. I took one for the team that day though.