Swiss stuntman Freddy Nock isn't afraid of heights, and he has proof: he just climbed Germany's highest mountain by tightrope walking up it's 1,000-meter-long cable car cable.
He did this all without a net, safety hardness or balancing pole. Why? I do not know. But he did it without falling off and splattering himself all over the rocks below, which I think makes it a success.
Here's a video of part of his ascent; get your palms ready to sweat.