You can see the Mathematical Bridge from Silver Street (it is across the street from The Anchor Pub). The original bridge was built in 1747 and rebuilt in 1866 and 1905.
Some gullible tourists have been told that it was built by Isaac Newton but he died in 1927. They have also been told that the bridge was originally built without screws and that one day students took it apart to see how it could hold itself together without screws. It has always had some sort of screws or bolts to help hold it together.