What name is common to a cathedral city in eastern England and a river flowing through Cardiff, Wales?

The River Ely flows through South Wales from Tonyrefail to Cardiff and shares its name with a cathedral city in Cambridgeshire, England. The river is approximately 24 miles (39 km) long and flows in a southeasterly direction.

Despite problems with pollution, the river is home to a number of different fish. These include roach, trout, perch, eels and salmon. In recent years, the Countryside Council for Wales and Cardiff Council have been developing a cycleway beside the river known as the Ely Trail to provide city dwellers with easier access to the countryside.

The origin and meaning of the name Ely is unknown but may derive from the Old Northumbrian word 'ēlġē', meaning "district of eels". The River Ely is home to many eels, as are the marshes and meres surrounding the city of Ely. Eels were an important source of income and food in both areas.

Ely Cathedral, officially called the Anglican Cathedral Church of the Holy and Undivided Trinity, was completed in 1351, but construction began in 1038 under William the Conqueror.