The price tag for Boston's Big Dig ballooned from $2.6 billion to nearly $15 billion. And it was eight years behind schedule by the time it was done. How does that compare with some other mega construction projects around the world?
Gotthard Base Tunnel, Switzerland
Cost: $10 billion. At 35 miles, the tunnel in the Swiss Alps is the longest in the world. Scheduled to open in 2016. (At right, a worker exits an access tunnel for the project in Erstfeld, Switzerland, in this 2011 photo.)
Alaskan Way Viaduct, Seattle
Cost: $3.1 billion. Earthquake-damaged highway to be replaced by a tunnel. Under construction. (In this 2013 photo, a surveyor works in a tunnel that is part of the Seattle project.)
D.C. Metro Silver Line extension
Cost: $7 billion. New 23-mile rail line to Dulles International Airport. Under construction. (At right, riders wait for a train to depart a Metro station in Arlington, Virginia, in a 2007 photo.)
Cost: $23 billion. New city rail lines, 13-mile tunnel. Under construction. (A worker walks through a partially completed CrossRail station tunnel in this 2014 photo.)
Second Avenue subway, New York City
Cost: $4.4 billion. New 8.5-mile transit line in Manhattan. Under construction. (Welders, shown in a 2014 photo, connect iron support bars during construction for the Second Avenue subway project.)
The Chunnel, English Channel
Cost: $21 billion. A 31-mile rail tunnel connecting England and France. Completed in 1994. (The Chunnel work site in Dover, England, is shown at right in a 1990 photo.)
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