Boston's Big Dig was one of the most ambitious engineering projects in history, but in 2006, a fatal collapse in one of its tunnels put the ambitious project in doubt; experts reveal what caused this engineering disaster and how it was fixed.

Montreal's Olympic Stadium was an ambitious engineering project with a striking Space Age design, but it's distinctive roof has caused over one billion dollars in cost overruns; experts reveal what went wrong and how cutting-edge science can fix it.