I've Never Been to the Very Top of Any Really Tall Building Before

I don't have a big fear in general of just being high in the sky. I've never been to the very top of any really tall building before, but I would be interested in going to the Burj Khalifa. The takeoff is the point when the airplane leaves the ground and it starts to go up into the sky. So, this is the part that freaks me out the most about flying.