Llyn Crafnant viewed from the summit of Crimpiau. Photograph by Terry Hughes
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Llyn Crafnant is a lake that lies in a beautiful valley in North Wales where the northern edge of the Gwydir Forest meets the lower slopes of the Carneddau mountains. The head of the valley offers a profile of crags which are silhouetted at sunset, and many people regard the lake as one of the most beautiful spots in North Wales. Indeed, the Forest Park guide (2002) states that "the (view along Llyn Crafnant) is one of the most breathtaking views in all Snowdonia." At 63 acres it is the best part of a mile long, although it was clearly once much longer - its southern end shows the evidence of centuries of silting. Jehu’s survey (see references) recorded a maximunm depth of 71 ft.

Crafnant takes its name from “craf”, an old Welsh word for garlic and “nant”, a stream. Even today the valley of Afon Crafnant smells of wild garlic when it flowers.

The lake can be reached by car only from Trefriw in the Conwy valley, though many visitors walk there from the village or from the neighbouring lake of Llyn Geirionydd, which runs parallel to it, but a mile distant, the two being separated by Mynydd Deulyn – “mountain of the two lakes”. Walkers also approach the lake from Capel Curig.

There is a Forestry Commission car park with toilets, which is reached just before the lake itself, and the lakeside cafe (open from Easter until late summer) offers car parking for patrons. The lake is a popular fishing spot, and the lake are kept stocked with brown trout and rainbow trout. From the cafe it is possible to hire boats for fishing or for pleasure. Private boating and swimming is not permitted.

The lake is a reservoir, and was dammed at its northern end in 1874, but the dam itself is barely visible as the outflow plunges down steeply from it. By the outflow is an obelisk, erected in 1896 by the inhabitants of Llanrwst which commemorates "the gift to that town of this lake with 19 acres of land" by Richard James. The fact that the lake no longer serves this purpose means that the inhabitants of Llanrwst and Trefriw have nowadays to pay for their water like everyone else. The lake itself is also no longer owned by the inhabitants of the village since it was leased to the owners of what is now the cafe.

In the upper part of the valley there is no mains water connection and during the particularly dry summer of 2006 many properties were without water.

The River Crafnant ("Afon Crafnant" in Welsh) joins the River Conwy at Trefriw, but not before some of it has been diverted to pass through the woollen mills to generate hydro-electricity for the mill.