Bay Bridge, San Francisco

When it was built in 1936, the San Francisco-Oakland Bay Bridge was something of a design marvel.

To span the gap between San Francisco and Oakland two separate spans connecting to Yerba Bueno Island (YBI) were required.

The West Span in the deep waters of San Francisco as suspension bridge was needed, in fact two suspension bridges. That's one of them in my photo.

The East Span required a truss-cantilever design to cover the shallow mudflats closer to Oakland.

Then as if that wasn't enough, there needed to ba a tunnel, a 76ft wide tunnel, on YBI to connect the two spans.

I think that qualifies as a design marvel.

Reference:
Bay Bridge History, The San Francisco-Oakland Bay Bridge website