Overview: 'National Geographic Channel MegaStructures' takes a look at the construction history of Boston Big Dig project. Costing almost 15 billion dollars and taking almost 20 yrs to complete, the Boston's Big Dig is considered to be the most complex, expensive, and technically challenging civil engineering public works project in the United States. The project was inspired by Fred Salvucci, the Transportation Commissioner to the Mayor of Boston, who wanted to find a solution to the city’s traffic woes. He came up with an idea to link up the major sectors of the city with a system of wide underground tunnels for traffic. Consisting of 4 elements, a tunnel under the harbor, an underground connection to the Interstate 90, an underground traffic system under the city itself to replace the elevated city highway, and a wide cable-stayed bridge to replace the old double-decked bridge. The episode looks at the many obstacles that were faced in the construction, from water leaks to residential protest. The episode also contains brief words from some of the major people involved in the project.