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.
- Small lakes, such as Llyn Ogwen, Llyn Safaddan (Llangorse Lake), Talyllyn, the Teifi Pools, &c., are fairly numerous in the mountainous districts, but the only natural lake of importance is Bala Lake, or Llyn Tegid, in Merionethshire, 4 m.
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.
Cardigan, in Welsh Aberteifi, from its situation near the mouth of the Teifi, and Brecon, in Welsh Aberhonddu, from its site near the confluence of the Usk and Honddu, are examples of corrupted Welsh names in common use - Ceredigion, Brychan - which possess in addition pure Celtic forms. In the third division, English place-names are tolerably frequent everywhere and predominate in the Marches and on the South Wales coast.
By far the larger portion of Wales is purely agricultural in character, and much of the valley land is particularly fertile, notably the Vale of Glamorgan, the Vale of Clwyd and the valleys of the Towy, the Teifi, the Usk and the Wye, which have long been celebrated for their rich pastures.
The Wye, the Usk, the Dee, the Dovey, the Teifi, the Towy and most of the Welsh rivers and lakes are frequented by anglers for salmon and trout.
At the accession of William Rufus the domain of Gwynedd had been reduced to Anglesea and the Snowdonian district, and that of South Wales, or Deheubarth, to the lands contained in the basins of the rivers Towy and Teifi, known as Ystrad Tywi and Ceredigion.
A fierce engagement took place wherein the Norman and Flemish troops were utterly routed, and the victorious Cymry slew thousands of their fugitives at the fords of the Teifi close to the town of Cardigan.
Of wholly Welsh rivers only the Towy and the Teifi are comparable in length and drainage area with the smaller rivers in the above list (see Wales).