We recently took a vacation to Gatlinburg and the guys decided they wanted to zipline!:/ Austin has no fear of heights. I asked him was he even a little scared before he went from Mountain top to Mountain top and he said not at all. I would've been shaking.
The scary part was when the doors flew open to the cabin while they were there and a storm came. They were able to get off and didn't finish the last two, but had fun on the experience.