Mwdwl-eithin is a gently rising mountain about 10 miles (16.1 km) east of Betws-y-Coed

Betws-y-Coed

Betws-y-Coed is a village and community in the Conwy valley in Conwy County Borough, Wales. It has a population of 534. The name Betws or Bettws is generally thought to be derived from the Anglo-Saxon Old English 'bed-hus' - i.e. a bead-house - a house of prayer, or oratory...

 lying on the Denbigh Moors (Mynydd Hiraethog in Welsh) of North Wales

North Wales

North Wales is the northernmost unofficial region of Wales. It is bordered to the south by the counties of Ceredigion and Powys in Mid Wales and to the east by the counties of Shropshire in the West Midlands and Cheshire in North West England...

 (the highest point) reaching a height of 532 metres (1,745 ft). On its summit is a trig point

Triangulation station

A triangulation station, also known as a triangulation pillar, trigonometrical station, trigonometrical point, trig station, trig beacon or trig point, and sometimes informally as a trig, is a fixed surveying station, used in geodetic surveying and other surveying projects in its vicinity...

 and a ruined building which still provides shelter against a storm. A few metres away is a large raised stone cairn

Cairn

Cairn is a term used mainly in the English-speaking world for a man-made pile of stones. It comes from the or . Cairns are found all over the world in uplands, on moorland, on mountaintops, near waterways and on sea cliffs, and also in barren desert and tundra areas...

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The whole area is underlain by Silurian

Silurian

The Silurian is a geologic period and system that extends from the end of the Ordovician Period, about 443.7 ± 1.5 Mya , to the beginning of the Devonian Period, about 416.0 ± 2.8 Mya . As with other geologic periods, the rock beds that define the period's start and end are well identified, but the...

 mudstone

Mudstone

Mudstone is a fine grained sedimentary rock whose original constituents were clays or muds. Grain size is up to 0.0625 mm with individual grains too small to be distinguished without a microscope. With increased pressure over time the platey clay minerals may become aligned, with the...

 which was extensively glaciated during the last British glaciation. The whole area is now very wet moorland dominated by heather (Calluna

Calluna

Calluna vulgaris is the sole species in the genus Calluna in the family Ericaceae. It is a low-growing perennial shrub growing to tall, or rarely to and taller, and is found widely in Europe and Asia Minor on acidic soils in open sunny situations and in moderate shade...

and Erica

Erica

Erica ,the heaths or heathers, is a genus of approximately 860 species of flowering plants in the family Ericaceae. The English common names "heath" and "heather" are shared by some closely related genera of similar appearance....

spp.) and rushes

Juncus

Juncus is a genus in the plant family Juncaceae. It consists of some 200 to 300 or more species of grassy plants commonly called rushes...

. Three of the surrounding valleys and depressions have been used for drinking water storage reservoirs, Llyn Alwen

Llyn Alwen

Llyn Alwen is a small upland lake on the Denbigh moors in North Wales at SH 898 565.It lies on the rolling Silurian moorland to the north-west of Mwdwl-eithin and about 10 km to the east of Betws y Coed. The discharge from the lake flows under the A543 road to form the headwater of Alwen...

, Llyn Aled and Alwen Reservoir

Alwen Reservoir

The Alwen Reservoir or Cronfa Alwen is a 5km long reservoir near Pentre-Llyn-Cymmer in the county borough of Conwy, North Wales, held back by the 27 metre high Alwen Dam. It impounds the Afon Alwen, and the dam is 8km downstream from Llyn Alwen. It was built between 1909 and 1921, originally to...

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