Llanthony Priory. Antique print of Llanthony Priory, also known as Lanthony Abbey is a partly ruined former Augustinian priory in the Vale of Ewyas, a steep sided once glaciated valley in Monmouthshire, south east Wales, Formerly in the county of Gloucestershire. Antique copper-plate engraving dated in the plate 19 June 1784. Size of engraved area approx 5x6ins. .