Dinefwr Park National Nature Reserve is an 800 acres (320 ha) estate about a mile from the centre of Llandeilo in Carmarthenshire owned by the National Trust, with a mansion in the centre. The highest point is occupied by the ruined Dinefwr Castle, ancient castle of the Deheubarth kingdom. It is a grade I Historic Park and a Site of Special Scientific Interest.

Llandeilo is a town and community in Carmarthenshire, Wales, situated at the crossing of the River Towy by the A483 on a 19th-century stone bridge. Its population was 1,795 at the 2011 Census. It is adjacent to the westernmost point of the Brecon Beacons National Park. The town is served by Llandeilo railway station on the Heart of Wales Line.