this is the original galloping gertie's 1940 bridge. you can see the two eight-foot-deep section. >> many lessons are learned from gertie's demise, including how critical aerodynamics are in building suspension bridges. >> there really wasn't a major suspension bridge built until the replacement in 1950. and many of the things that exist on the 1950s bridge are a tribute to better aerodynamic stability. >> in 2007 a twin bridge is completed. the architectural look of both structures resembles the original gertie, a tribute to her grace and elegance. >> so that new bridge as well as others have been constructed since 1940 are part of galloping gertie's legacy. >>> coming up -- an iceberg implodes in front of a group of tourists sending them scrambling for safety. >> we're all shouting and screaming. >> when "caught on camera: watch out" continues. it starts with something little, like taking a first step. and then another. and another. and if you do it. and your friends do it. and their friends do it... soon we'll be walking our way to a