Ely is built on a 23-square-mile (60 km2) Kimmeridge Clay island which, at 85 feet (26 m), is the highest land in the fens. Major rivers including the Witham, Welland, Nene and Great Ouse feed into the fens and, until draining commenced in the 17th century, formed freshwater marshes and meres within which peat was laid down. There are two Sites of Special Scientific Interest in the city: a former Kimmeridge Clay quarry, and one of the United Kingdom's best remaining examples of medieval ridge and furrow agriculture.
The economy of the region is mainly agricultural. Before the fens were drained, the harvesting of osier (willow) and sedge (rush) and the extraction of peat were important activities, as were eel fishing—from which the settlement's name may have been derived—and wild fowling. The city had been the centre of local pottery production for more than 700 years, including pottery known as Babylon ware. A Roman road, Akeman Street, passes through the city; the southern end is at Ermine Street near Wimpole and its northern end is at Brancaster. Little direct evidence of Roman occupation in Ely exists, although there are nearby Roman settlements such as those at Little Thetford and Stretham. A coach route, known to have existed in 1753 between Ely and Cambridge, was improved in 1769 as a turnpike (toll road). The present day A10 closely follows this route; a southwestern bypass of the city was built in 1986. Ely railway station built in 1845 is on the Fen Line and is now a railway hub, with lines north to King's Lynn, northwest to Peterborough, east to Norwich, southeast to Ipswich and south to Cambridge and London.
The King's School is a coeducational boarding school which was granted a royal charter in 1541 by Henry VIII; the school claims to have existed since 970. Henry I granted the first annual Fair, Saint Audrey's (or Etheldreda's) seven-day event, to the abbot and convent on 10 October 1189; the word "tawdry" originates from cheap lace sold at this fair. Present day annual events include the Eel Festival in May, established in 2004, and a fireworks display in Ely Park, first staged in 1974. The city of Ely has been twinned with Denmark's oldest town, Ribe, since 1956. Ely City Football Club was formed in 1885.
Roswell Pits are a palaeontologically significant Site of Special Scientific Interest (SSSI) one mile (1.6 km) northeast of the city. The Jurassic Kimmeridge Clays were quarried in the 19th and 20th centuries for the production of pottery and for maintenance of river embankments. Many specimens of ammonites, belemnites and bivalves were found during quarrying, in addition to an almost complete specimen of a pliosaur.
There is some scattered evidence of Late Mesolithic to Bronze Age activity in Ely such as Neolithic flint tools, a Bronze Age axe and spearhead. There is slightly denser Iron Age and Roman activity with some evidence of at least seasonal occupation. For example, a possible farmstead, of the late Iron Age to early Roman period, was discovered at West Fen Road and some Roman pottery was found close to the east end of the cathedral on The Paddock. There was a Roman settlement, including a tile kiln built over an earlier Iron Age settlement, in Little Thetford, three miles (5 km) to the south.