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The River Cam is a tributary of the River Great Ouse in the east of England. The two rivers join to the south of Ely at Pope's Corner. The Great Ouse connects the Cam to England's canal system (via the Middle Level Navigations and the River Nene) and to the North Sea at King's Lynn. The total distance from Cambridge to the sea is about 40 mi (64 km).

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The Mathematical Bridge is the popular name of a wooden footbridge that crosses the River Cam; about one hundred feet northwest of Silver Street Bridge and connects two parts of Queens' College. Its official name is simply the Wooden Bridge.
The bridge was designed by William Etheridge, and built by James Essex in 1749. It has been rebuilt on two occasions, in 1866 and in 1905, but has kept the same overall design. Although it appears to be an arch, it is composed entirely of straight timbers built to an unusually sophisticated engineering design, hence the name.
The original "mathematical bridge" was another bridge of the same design, also commissioned by James Essex, crossing the Cam between Trinity and Trinity Hall colleges, where Garret Hostel Bridge now stands.
The Bridge is Grade II listed. Link

Queens' College is a constituent college of the University of Cambridge. Queens' is amongst the oldest and largest colleges of the university, founded in 1448 by Margaret of Anjou (the Queen of Henry VI, who founded King's College), and has some of the most recognisable buildings in Cambridge. The college spans both sides of the river Cam, colloquially referred to as the "light side" and the "dark side", with the world famous Mathematical Bridge connecting the two.
Wikipedia: Link
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The following is a list of the bridges in Cambridge, mainly those over the River Cam.
Bridges over the River Cam (south to north) :

Footbridge, Coe Fen
Fen Causeway Bridge
Crusoe Bridge
Darwin College Bridges
Silver Street Bridge (1958)
Mathematical Bridge, Queens' College (1902)
King's College Bridge (1819)
Clare College Bridge (1640)
Garret Hostel Bridge (1960)
Trinity College Bridge (1764)
Kitchen Bridge, St John's College (1709-11)
Bridge of Sighs, St John's College (1831)
Magdalene Bridge (1823)
Jesus Lock footbridge (1892)
Victoria Avenue Bridge (1890)
Footbridge, Midsummer Common
Cutter Ferry Bridge
Elizabeth Way Bridge (1971)
Riverside Bridge (2008), renamed Equiano Bridge 2022
Green Dragon footbridge, Stourbridge Common
Railway Bridge
Abbey-Chesterton Bridge (2022)
A14 Bridge
Footbridge over the weir, Baits Bite Lock

Wikipedia article:
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Listed buildings and structures are officially designated as being of special architectural, historical or cultural significance. There are over half a million listed structures in the United Kingdom, covered by around 375,000 listings.
Listed status is more commonly associated with buildings or groups of buildings, however it can cover many other structures, including bridges, headstones, steps, ponds, monuments, walls, phone boxes, wrecks, parks, and heritage sites, and in more recent times a road crossing (Abbey Road) and graffiti art (Banksy 'Spy-booth') have been included.

In England and Wales there are three main listing designations;
Grade I (2.5%) - exceptional interest, sometimes considered to be internationally important.
Grade II* (5.5%) - particularly important buildings of more than special interest.
Grade II (92%) - nationally important and of special interest.

There are also locally listed structures (at the discretion of local authorities) using A, B and C designations.

In Scotland three classifications are also used but the criteria are different. There are around 47,500 Listed buildings.
Category A (8%)- generally equivalent to Grade I and II* in England and Wales
Category B (51%)- this appears generally to cover the ground of Grade II, recognising national importance.
Category C (41%)- buildings of local importance, probably with some overlap with English Grade II.

In Northern Ireland the criteria are similar to Scotland, but the classifications are:
Grade A (2.3%)
Grade B+ (4.7%)
Grade B (93%)

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