The Central Artery/Tunnel Project, also known as the Big Dig, was a major infrastructure project in Boston, Massachusetts. It aimed to reroute the elevated Central Artery highway into a tunnel, reducing traffic congestion and improving air quality in the city. The project included the construction of a new tunnel system and the creation of Rose Kennedy Greenway, a series of parks and public spaces. Completed in 2007, the Big Dig was one of the most complex and expensive highway projects in U.S. history, costing over $14 billion. It involved extensive engineering challenges, including the relocation of utilities and the management of groundwater. The project significantly transformed the urban landscape of Boston, enhancing both transportation and public spaces.