Llyn Pencarreg is an unusual example of a lowland 'oligotrophic' (very nutrient poor) lake of glacial origin, now designated as a Site of Special Scientific Interest. It lies alongside the Roman road (RR 69d Carmarthen-Llanio).

It is recorded that; 'At one spot near the Llyn what is described as the head of an iron mace was found on the surface of the road' (RCAM Carms Inventory 1917, 207).

This is an interesting record as it may relate to a later prehistoric macehead rather than a Roman example. It is noted as being found on the surface of the road, but its close association to the lake may indicate potential votive use of the lake in the later prehistoric or Roman period.

Two Iron Age hillforts overlook the lake, Pen y Gaer Llanybydder (NPRN 303873) and Blaen-maes Hillfort, Pencarreg (NPRN 402874).

T. Driver, RCAHMW, 2014

See also:
B.B.C.S., 4, 1927-9. 254 (Nash-Williams).