The scenery of the neighbourhood, in both the Wye and the Derwent valleys, is very beautiful; the village of Eyam (pronounced Eem) near the Derwent may be noticed as specially picturesque.
The name of Wye belongs also to two smaller English rivers - (I) a right-bank tributary of the Derbyshire Derwent, rising in the uplands near Buxton, and having part of its early course through one of the caverns characteristic of the district; (2) a left-bank tributary of the Thames, watering the valley of the Chilterns in which lies Wycombe and joining the main river near Bourne End.
Past Wye and Canterbury, to meander through the lowlands representing the former channel which isolated the Isle of Thanet from the mainland.
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.
The scenery of the Wye valley, including a succession of rapids just above the town, also attracts many tourists.
Plinlimmon (2468 ft.) is the highest of the hills, and forms a sort of hydrographic centre for the group, as from its eastern base the Severn and the Wye take their rise - the former describing a wide curve to east and south, the latter forming a chord to the arc in its southward course.
Towards the end of the 11th century, when the tide of Norman invasion swept upwards along the Wye valley, the district became a lordship marcher annexed to that of Brecknock, but was again severed from it on the death of William de Breos, when his daughter Matilda brought it to her husband, Roger Mortimer of Wigmore.
But the most important result of this first Norman invasion was to be found in the marvellous and rapid success of Robert Fitz-Hamon, earl of Gloucester, who, accompanied by a number of knightly adventurers, quickly overran South Wales, and erected a chain of castles stretching from the Wye to Milford Haven.
Rhayader, built close to the Falls of the Wye (whence its name), owes its early importance to the castle erected here by Prince Rhys ap Griffith of South Wales, c. 1178, in order to check the English advance up the Wye Valley.
To the south-east of this region a narrow outcrop of Upper Llandovery, Wenlock and Ludlow sandstones and mudstones follows, uncomformably overlying the Llandeilo and Bala rocks, and dipping conformably under the Old Red Sandstone; they extend from Newbridge-on-Wye and Builth through Llangammarch (where there are mineral springs) towards Llandovery, while a tongue of Ludlow rocks brought up by faulting extends from Erwood on the Wye for 8 m.