The Mathematical Bridge is the famous wooden footbridge at Queens’ College, Cambridge, which appears as a graceful arch even though it is built entirely from straight timbers. It is a Grade II listed structure and one of the most recognisable sights on the River Cam, linking the older riverside buildings of Queens’ with later college accommodation across the water.
 
It's actually much older than it looks designed in 1748 by the engineer William Etheridge and built in 1749 by the carpenter James Essex the Younger. Although it has been rebuilt twice! 
 
The form is rather clever timber works best then compressed or in tension but weaker if bent. The form of the bridge keeps each member in compression or tension -neat.
 
Interesting facts....
There were actually two but the other collapsed. Oh and the rumours are that Isaac Newton designed it are wrong, he didn't live that long