Like many ruined religious buildings in England and Wales, Llanthony Priory was abandoned around 1540 following the Dissolution of the Monasteries, instigated by Henry V. A Catholic (Augustine) settlement was established at the site around 1100 by a Norman, William de Lacy, who drew inspiration from the small ruins of an earlier chapel, and the dramatic setting, in a remote, narrow, glaciated valley, the Vale of Ewyas, which is enclosed on both sides by the steep slopes of the Black Mountains, the easternmost component of the Brecon Beacons. The initially small church was expanded and augmented in several stages, designated a priory in 1118 and reaching a peak in the 14th and 15th centuries, and was unusually large and impressive for such an out-of-the way location. A priory is a monastery managed by a prior, as opposed to an abbey which is managed by an abbot. Since the dissolution, Llanthony Priory gradually became derelict, in part due to the often harsh weather, but parts were still used and maintained, initially as a residence and now as a guest house, the Llanthony Priory Hotel.
The priory is located towards the north end of the Vale of Ewyas, along one of several scenic routes between Abergavenny and Hay-on-Wye. For over ten miles the road runs along the floor of the valley, close to the River Honddu, until, at the upper end, a little way north of the priory, it climbs to Gospel Pass - the highest pass in Wales - then descends towards open farmland around the River Wye. The road is narrow, bordered by walls or high verges, and is often wide enough for only one vehicle, though the traffic is generally light. A few settlements are scattered along the valley floor, but most of the surroundings are woodland and green fields, lined by walls constructed of the same dark, reddish-grey rock that was used for the priory.
A short side road leads to the hotel and its parking area, which is also used for visitors to the adjacent ruins. The site is managed by Cadw (Welsh Heritage), and admission is free. Other structures here include the intact, twelfth century St David's Church, an old barn used for guest lodging (Llanthony Court) and several farm enclosures, though the scene is dominated by the priory, the main part of which is orientated approximately east to west.
Visitors approach from the south, across the cloister, a square, grassy courtyard bordered on one side by the hotel and on the other by low wall remnants of the chapter house, which was used for business and administration, and is separated from the main church by a narrow passageway with a vaulted roof, known as a slype. To the north are two lines of columns and arches, forming the side walls of the nave, the longest section of the priory, which leads to two towers on the west side - one incorporated into the hotel, and the largest surviving section to the east; this includes the choir, with the presbytery beyond, and the north and south transepts on either side. These are linked to wall foundations from several small chapels that once adjoined the main structure.
All the ruins have wonderfully aged masonry, flecked with lichen, extensive black patina, and occasional small plants, and are characterised by wide arches, isolated columns, and the verdant green grass underneath, all enhanced by the stark but beautiful surroundings.