<Tr> <Th> Length </Th> <Td> 64.0 km (40 mi) </Td> </Tr> <P> The River Taff (Welsh: Afon Taf) is a river in Wales . It rises as two rivers in the Brecon Beacons--the Taf Fechan (Little Taff) and the Taf Fawr (Big Taff)--before joining to form the Taff north of Merthyr Tydfil . The river supports a number of migratory fish, including salmon, sea trout, and eel . </P> <P> From its confluence at Cefn - coed - y - cymmer, the river flows south, passing several towns . It picks up a few tributaries, such as the River Cynon, River Rhondda, Bargoed Taf and Nant Clydach . It flows through Pontypridd and through to Taff's Well, the site of Wales' only thermal spring . It flows underneath the M4 Motorway, before turning southeastward and flowing through the Cardiff suburbs of Radyr, Whitchurch, Llandaff, Pontcanna, the city centre and Grangetown, before emptying into Cardiff Bay, near to the mouth of the River Ely . </P> <P> In the early 1840s the South Wales Railway was trying to find a suitable site for a railway station, but the area that is now Cardiff Central railway station was prone to flooding . At this point the main route of the Taff was around Cardiff Castle and down what is now Westgate Street, with the lands where Cardiff Arms Park and the Millennium Stadium are now sited tidal flats which were prone to flood . </P>

Where does the river taff start and finish