The historical interest of the place centres in its proximity to the castle of Dinefawr, now commonly called Dynevor, which was originally erected by Rhodri Mawr or his son Cadell about the year 876 on the steep wooded slopes overhanging the Towy.
The place probably owes its Celtic name of Llan-ym-ddyffri (the church amid the waters) to the proximity of Llandingat church to the streams of the Towy, Bran and Gwydderig.
The Wye is the chief river, and forms the boundary between the county and Radnorshire on the north and north-east, from Rhayader to Hay, a distance of upwards of 20 m.; its tributary, the Elan, till it receives the Claerwen, and then the latter river, continue the boundary between the two counties on the north, while the Towy separates the county from Cardigan on the north-west.
From Plinlimmon a range of hills runs in a south-westerly direction towards St Davids, terminating in the Preselly range of north Pembroke (1760 ft.) and dividing the broad valleys of the Teifi and Towy.
The Towy (68 m.) flows through Carmarthenshire, entering Carmarthen Bay at Llanstephan; the Teifi (50 m.) rises near Tregaron and falls into Cardigan Bay below the town of Cardigan.