Banc Du is a prominent, fairly flat-topped southwards-projecting promontory of Foel Eryr, at about 334m OD at the west end of the Preseli Hills in north Pembrokeshire, Wales.
Neither upland not lowland, Banc Du occupies a curious position between enclosed fields and open moor, clearly cultivated in the past, but now maintained as improved pasture for grazing sheep.
The most recent comprises extensive ridge and furrow cultivation probably associated with a now-abandoned, putatively medieval or later, long house settlement or small hamlet downslope to the north-west.
Examination of pollen evidence concludes that the enclosure was built in a heath-dominated landscape with some local scrubby woodland including oak and hazel.
The first confirmed neolithic enclosure in Wales and the mid west of Britain, it is also notable for the fact that visible earthworks survive at ground level.