Here are four examples, in one iPhone photo, of why I love this city and its august architectural/engineering lineages. On the left is the North Bank Bridge, a 700-foot-long footbridge that was opened last year to much fanfare. It connects Cambridge to Charlestown, and cuts the walk time between the two down from thirty minutes to five. Its sinewy, sinusoidal look isn’t just for aesthetics, though I’d still think it was a marvelous structure if that were the case (it’s beautiful enough that it’d be justified). The “sinusoidal” effect is actually from the trusses weaving below the bridge to above it and below again--- they dip below to create more space between the highway overpasses above them, then swing above to make more room for the commuter rail tracks passing beneath.
In the far background, of course, is the Zakim Bridge (or the “Leonard P. Zakim Bunker Hill Memorial Bridge,” if you want to get all fancy). From an engineering standpoint, it’s astounding: it’s the widest cable-stayed bridge on the planet (the bridge deck is 183 feet across, carrying 10 lanes), and it was the first cable-stayed bridge with an asymmetrical deck design. The pylons echo the nearby Bunker Hill Monument, and the white cables streaming down to the deck bring to mind the rigging of the USS Constitution, which is just down the harbor a bit.
A little closer (in front of the Zakim Bridge, middleground) is the Leverett Circle Connector Bridge. It might not look like all that much, but it’s the largest steel box girder bridge in the United States. It connects to I-93 in Somerville in the north, and to Storrow Drive and Leverett Circle (two high-volume Boston spots) in the south.
Finally, in the near-right, is the Boston & Maine Charles River Bridge. Built in 1931, this is one of the only functioning rolling-bascule bridges in the country, and it still works perfectly. All of the North Station Commuter Rail lines—almost 30,000 people every day—pass over this bridge, and it’s never failed. It’s beautiful, functional, and incredibly simple—the whole thing just rotates on a counterweight.