I didn't think I was afraid of heights. As a kid, common activities included jumping off barns, climbing up silos, walking on weird rope bridges, climbing precarious trees.
But take me to the top of Pyramid Mountain: now that's a different story.
At that height and the mountain/valley terrain, the wind is always blowing -- hard. You have only a foot or so of earth on either side of you before a sheer cliff that drops down an ungodly amount of unsurvivable feet.
Yeah, sure, the 360-degree view is spectacular but holy cow, let me sit down!