This reservoir formed part of Aberllefenni Slate Quarry (NPRN 40584) and supplied water to power Aberllefenni Slate Mill (NPRN 408514). It survives relatively intact and encompasses an area roughly 9 m square, complete with a stone dam, across which the Ratgoed Tramway once ran. The reservoir was fed directly from the Afon LLefeni, with water diverted to the mill via a series of sluice gates and slate lined leats. Excess water ran out over a weir and down into the Afon Dulas.

Louise Barker, RCAHMW, June 2010