I saw a TV programme about how they made the glass platform over the canyon, it looks awesome, I'd love to go there too. I was lucky enough to go up to the top of the WTC in 1992, I didn't really think anything of it at the time, but after 9/11 I found myself looking at my photo's of the Manhattan skyline and realising how much it had dominated the skyline.
I'm sure there is a walkway of some sorts at Taipai 101 which I believe is currently the worlds tallest building, until the Burj Tower in Dubai is completed (I'm sure someone will correct me if my facts are wrong
). Flying into Dubai, the Burj Tower construction site is very impressive, it stands about twice as tall as anything else in the city. I wonder how long it will take until someone base jumps off the top of the Burj