Llyn Dulyn (Welsh: Black lake) is a lake on the edge of the Carneddau range of mountains in Snowdonia, North Wales. The lake covers an area of only 33 acres (130,000 m2), yet is extremely deep - it reaches to a depth of 189 feet (58 metres). Less than a kilometre to its south lies the smaller Llyn Melynllyn. Cliffs rise steeply from the lake edge up to the summits of Garnedd Uchaf and Foel Grach, giving it a dark brooding appearance - hence its name. A number of superstitions are connected with the cwm, which has also been the site of a number of small aeroplane crashes.