I often think about bridges. Especially when I'm tinkering with a problem that I find challenging. It reminds me building a bridge would be much harder. And it's been done many times before.
What strikes me in the construction of massive structures such as bridges is the gap between the vision and the actual work. You need to be extremely convinced and convincing to get people behind the idea.
I'm not an engineer. I'm not a builder. But I'm sure I can learn a thing or two from the guys who built them hundreds of years ago.
Here's a cool video I found on Vimeo (a platform where we should spend much more time by the way) about the Brooklyn Bridge in New York.