When it came to building or improving things, the ancient Romans really knew their stuff. Which cool engineering tricks did they pass along to us?
It took years to construct the 110-story World Trade Center towers and less than an hour to bring them down to rubble. What ultimately caused the towers to collapse on Sept. 11, 2001? See more »
The materials used to build the World Trade Center's twin towers have been heavily scrutinized since the 9/11 terrorist attacks -- including the steel that formed the frames of the skyscrapers. See more »