Its actually fairly rare that you can call engineering beautiful. Engineering can produce beautiful things, but the widget or construction itself doesn't often come to mind. However, you must check this out. A new bridge in France that is really breath taking. We'll ignore the question of "why" for a moment (it does seem a bit excessive), but it really is a photogenic bridge.
In the same vein, can you imagine the span between San Francisco and Marin County without the Golden Gate?
There was a Discovery channel special on the GGB that I caught a few months ago with some photos of the Bay without the bridge, and it just wasn't the same. Although, I'm definitely not arguing that all bridges add to the surrounding landscape -- it's probably the exception, rather than the rule -- but unlike dams, highways, and other civil engineering projects, a well done bridge seems to add more than it detracts.