America has a new engineering wonder close to the Hoover Dam.  Opened earlier this month, the Mike O'Callaghan-Pat Tillman Memorial Bridge stretches over the Colorado River at a height of 890 feet and is part of a project to allow commercial traffic to reach the Las Vegas area without taking the narrow, hairpin curved two lane highway that runs along the top of the dam.  This will speed traffic and allow tourists faster access to the region, which draws millions every year.  After 9/11, the Feds worried that a truck bomb could be used to damage or destroy the Hoover Dam and flood the area while disrupting power to several states.  It took five years to build and is now the seventh highest bridge in the world.