Iron Age Hillfort
Llanymynech hillfort, Powys (SJ267227) “Excavation in the area of the N gate, prior to drainage improvements, revealed a third, unsuspected rampart between the inner and outer defences. Its badly-destroyed remains, comprising a dump of limestone blocks c.2.8m wide, were set into a slight scoop in the hillside, overlying an earlier wall of igneous stone. There was no evidence for any associated ditch, suggesting haste in its construction, to be connected perhaps with the additum vallum described by Tacitus in the context of the final battle against Caratacus (Annals XII.35).”
Above quote from Britannia xxvi (1995) p.328.
Map References for Llanymynech – Powys
NGRef: OSMap: LR126