Llwyn Bryn-dinas (SJ 172247; Clwyd Archaeological Record CAR 999) is the only hillfort of substance in this part of the Tanat Valley, lying almost midway between the major forts of Craig Rhiwarth and Llanymynech Hill (fig. 1). Craig Rhiwarth, enclosing an area of about 35 ha/86 acres, lies above Llangynog, about 12 km to the west, where the head of the valley cuts into the rugged uplands of southern Clwyd. The very large hillfort on Llanymynech Hill (56 ha/140 acres) lies about 9 km to the east, near the confluence of the Tanat and Vymwy, which feed into the Severn a little furtherdownstream. Two smaller neighbouring sites of later prehistoric type are known from aerial photography - a small double-ditched enclosure known as Plas Uchaf, on a hillock at the very foot of Llwyn Bryn-dinas (SJ179245; CAR 1002), and a square double-ditched enclosure on the banks of the Tanat about 1.5 km to the south-west (SJ 156245; CAR 1433); both enclose about 1 ha/2.5 acres. The site now lies within th~ community of Llangedwyn, Clwyd, but before Local Government re-organisation in 1974 it fell within Llanrhaeadr-ym-Mochnant, Denbighshire.