7. Great Towers in the Sky

Viewer discretion is advised for those with vertigo! Featuring rare construction footage and interviews with steely-nerved iron workers who risked death to build them, we climb to the top of the world's tallest, most innovative, and most thrilling structures, including Seattle's Space Needle, Toronto's CN Tower, and Las Vegas's Stratosphere. The architects who designed these astounding buildings explain how each broke the boundaries of architecture at the time it was built.