The 'Mathematical Bridge' is the nickname given to a wooden footbridge that crosses the River Cam in the centre of Cambridge, England. The bridge, officially called the 'Wooden Bridge', was designed and built by William Etheridge and James Essex in 1749, and it connects two parts of Queens College. It has been rebuilt once in 1866 and again in 1905, but has always kept the same design - appearing to be an arch but actually constructed completely out of straight pieces of timber. The reason the bridge has been nicknamed the 'Mathematical Bridge' is because of its extremely precise and sophisticated design - placing the straight timbers at specific angles to give the impression of a curve.
There was another, original 'Mathematical Bridge', also designed by James Essex, that previously crossed the River Cam where the current 'Garret Hostel Bridge' is now located, between the Trinity and Trinity Hall Colleges.
There is a local story that states the Mathematical Bridge was originally built by Sir Isaac Newton, who did not use any nuts or bolts at all in the design of the bridge, and that a group of students once attempted to dismantle the bridge and put it back together again, but failed in their task and were forced to add nuts and bolts to re-build the structure. In reality, Isaac Newton died 22 years before the Mathematical Bridge was even built, so he couldn't have possibly had any hand in its creation, and nuts and bolts have always been a part of the bridges design.