Bridges are among the first things that come to mind when people around the world think of San Francisco, but how many of us know anything about them? Lucky for us, local architect Donald MacDonald is considered one of the world’s foremost experts on bridges. His firm helped with the Golden Gate Bridge’s seismic retrofit, and it has been instrumental in the construction of the Bay Bridge’s new eastern span. Once completed, it will be the world’s largest self-anchored suspension span, and new addition to our already spectacular skyline. The Bay Bridge’s younger and hotter sister, meanwhile, the Golden Gate Bridge, was also an engineering marvel — by 1937 standards. Today, MacDonald and the San Francisco Historical Society offer A Tale of Two Bridges, a boat tour where you can observe and learn about our two best-known bridges. Also included on the tour is a pass by Alcatraz, about which MacDonald also has extensive knowledge. He’s written books on the history and design of Alcatraz as well as the Golden Gate Bridge, which remains one of the most photographed structures in the world. We imagine you’ll take a few photos on this trip, but by day’s end you’ll know all about what you shot.
Sun., May 6, 1 p.m., 2012