Dolforwyn Castle is one of relatively few medieval fortifications in the Welsh Marches that were built by a Welsh prince, since the majority were English in origin. The castle was completed in 1277 under the stewardship of Llywelyn ap Gruffudd, Prince of Gwynedd, but it had been captured within the year, and then occupied for less than a century before being abandoned. The structure was more basic than a typical Norman castle, consisting of a low, rectangular enclosure with two small towers among the perimeter, and various rooms inside, but the setting was and is impressive, at the summit of a steep-sided ridge overlooking the River Severn, which in medieval times marked the boundary between England and Wales, a divide since moved further east.
The castle quickly became ruinous and overgrown, and received little attention for some 600 years, until late 20th century excavations, accompanied by repairs to the surviving foundations. The walls now have a smooth, somewhat artificial appearance, as much of the masonry is crisp and new, and the site is crossed by various railings and walkways, yet the location remains peaceful, isolated and atmospheric, with commanding views over a wide expanse of hills and valleys. Despite the partial rebuilding the ruins still have generally low relief in comparison to the overall size, of 230 by 100 feet; most of the internal walls are only between two and six feet tall, so the structure itself is not particularly distinctive, and looks broadly similar from all angles.
Llywelyn ap Gruffudd was the grandson of Llywelyn the Great, ruler of most of Wales at the start of the 13th century. The younger Llewellyn was the last native Prince of Wales, recognised as such by Henry III, in 1267, following the Treaty of Montgomery. The castle was intended to augment this new found authority, though it was built without permission, and partly because of this the place was soon besieged and captured, following a brief campaign led by Roger Mortimer (died 1287), and Dolforwyn stayed with the Mortimer family until 1332, when it was forfeited to the Crown. Occupation continued for a few more decades but the castle was reported as being empty and disused by 1398. The site was for much of the subsequent time owned by the Earls of Powis, until transfer to the state in 1955. Excavations and partial reconstruction work were completed by 2002; prior to this only a few, discontinuous wall fragments were visible, the rest buried under grass and soil, but now the lower walls of nearly all sections are visible once more.
The castle is accessed by an unnamed country lane that forks west off the A483 in the River Severn valley, 4 miles northeast of Newtown. The closest village is Abermule, just south of the intersection, near the bridge where the highway crosses the river. The small parking area for the castle is 0.7 miles from the A road, after turning left at the first junction, then from here the castle is reached by a quarter mile walk, gaining 200 feet, along an unpaved track, often muddy and slippery, that leads steeply uphill, past an isolated house (Yewtree), up to the ridgetop on the west side of the castle, and finally back east to the entrance. The slightly undulating area to the west was once the site of a small village, established by Llywelyn ap Gruffudd, but this was also soon abandoned, and the residents moved to the new settlement of Newtown. The name Dolforwyn ("maiden's meadow") refers to a nearby patch of grassland by the River Severn, supposedly the place where the mythical princess Hafren was drowned.
Dolforwyn Castle is protected by earthen banks; natural to the northwest and southeast, man-made on the other two sides. The entrance is on the southwest side, originally via a wooden bridge over a ditch, and into a narrow gateway, just beyond which are the remains of the rectangular keep, one of the earliest parts of the structure. Two small rooms adjoining the keep to the south were a guard chamber and a store. A passage leads round the opposite side to the main courtyard, which had a bakehouse, brewhouse and storeroom along the southeast wall, and the living area along the northwest, incorporating amongst other features a hall, chapel, D-shaped tower, bake oven, well and a vaulted cellar. The well was at least 20 feet deep and was added by the English, after the 1277 capture; lack of a internal water source was one of the reasons the Welsh were unable to survive the siege. At the centre of the northeast wall is the base of a round tower, the other main early component, originally of two stories. The southeast wall once contained a second, smaller gateway, but this was closed by the English.