Little Doward is just a few miles north of Monmouth. Not much remains at Little Doward from Vortigern's time; the years of forestry have covered up most of the ruins.
Vortigern, fled to one of his strongholds in Wales to escape St Germanus. He had a number of them from Gwynedd in the north, Dyfed in the west to this one, Little Doward, set high above a loop of the river Wye.
Nennius describes it as being located in the region of Gueneri or Guenessi (probably Gwent) but the location is far from being unequivocal. "Gueneri' could be Ganarew
Geoffrey of Monmouth gives Vortigern’s final refuge to have been Ganarew (Genoreu, Goronw) on the river Wye (Gwy, Gania) in Ercing (now Herefordshire). His Mons Cloartius is parhaps a variant for ‘Doartius’, Little Doward hill.
Historia Regum Britanniae, book VIII, chapter 2 "In pursuance therefore of this design, he marched with his army into Cambria, to the town of Genoreu, whither Vortigern had fled for refuge. That town was in the country of Hergin, upon the river Gania, in the mountain called Cloartius."
A Little Doward connection with the Arthurian souces in literature seems to depend on linguistic interpretation.
Arthurian Sites in Wales