The longest river which starts and finishes within the country of Wales is the River Tywi, sometimes referred to as the River Towy.
The River Tywi is 75 miles (120km) long and is Wales’ longest river.
River Tywi / River Towy
Afon Tywi, as the river is known in the Welsh language, begins on the slopes of Crug Gynan, which is a peak in Llanwrtyd Wells, a town in Powys.
From here the river flows for around six miles (10km) before reaching the large man-made reservoir and dark sky discovery site of Llyn Brianne.
The river passes to the nearby towns of Llandovery and Llandeilo in Carmarthenshire, before meeting several tributaries in the large market town of Carmarthen. From here the river flows all the way to Llansteffan, where it finally meets the sea at Carmarthen Bay.
The river is well known for its salmon and sewin fishing, whilst several castles overlook the river on its path through Carmarthenshire, such as Dinefwr Castle in Llandeilo and finally Llansteffan Castle, which provides some amazing views of the Twyi estuary.