Zakim Bunker Hill Memorial Bridge

Boston's iconic bridge is also its newest, and wouldn't be there were it not for the infamous traffic jams on the old Central Artery, the elevated section of I-93 that twisted through downtown Boston. The 15-year and $15-billion Big Dig was meant to alleviate that congestion by putting the artery underground; the project officially ended on Dec. 31, 2007, and the Zakim Bridge (named for a Boston civil rights leader) was part of the package. The eight-lane, cable-stayed bridge—the world's widest—carries traffic across the Charles River.