In the picture (at right): The suspension tower for the new eastern span of the San Francisco-Oakland Bay Bridge, viewed from the old cantilever span it will replace. The extensions to right and left of the tower are catwalks for ironworkers and others who will be involved in stringing the bridge's main suspension cable. (For context's sake: that tower is 525 feet tall, and the bridge deck I was driving on was about 200 feet above the water, meaning the tower's still out there in the distance a ways in this image.)
The new bridge will be a beauty, but the most arresting fact about it is how long it has taken to put up. The original Bay Bridge--both the eastern cantilever section and the immense double suspension section to the west--took about 40 months to build, from 1933 to late 1936. The new bridge has been under construction since 2002 and won't be done until 2013. And it was underwent about a decade of study and design work before the first hardhat was donned on the project. Lots of reasons for that--new understanding of the seismic complexity of the site, tougher environmental regulations, more complex logistics with so much of the material for the job coming from overseas (the tower sections and most of the other steel on the structure came from China, as did some of the key construction equipment).