The Three Castles in Monmouthshire, southeast Wales, are a group of early 13th century fortifications close to the River Monnow, which forms the present-day border with England; one (White Castle) is situated on a hill a few miles west, while the other two, at Skenfrith and Grosmont, are right beside the water. Of the three, Skenfrith Castle is intermediate in size and perhaps the least impressive to view owing to its rather basic design, though the ruins are still substantial, and rather different to the other two; an approximately rectangular outer wall, with towers at each corner, and a large, circular keep at the centre. Other visible structures are limited to a few rooms along the west side (the hall range), revealed only by relatively recent excavations. One of the towers is mostly missing, as is the entrance gate, and the moat that once circled the castle has long since been filled in, but the rest of the site is fairly complete. None of the walls or towers can be climbed so a tour may only take half an hour or so, yet the place is peaceful, scenic and well worth visiting.
Skenfrith is reached by the B4521, a narrow and winding road through hilly country, linking with the A446, three miles east. The castle is built on the outside of a bend along the River Monnow, here flowing through quite a deep valley flanked by partly wooded slopes rising up to 500 feet above. Parking is on a quiet residential street along the southwest side, from where the entrance is a short walk away to the north. There is no charge to visit, and the place is accessible at all times. The south side of the castle adjoins private land while the east parallels a belt of trees next to the river hence views from these directions are obscured, but the other two edges border open grassland. The first view is of the 160 foot-long southwest wall, which has a tower at either end and another in the middle; this is a later addition, probably installed towards the end of the 13th century, and is completely solid. The northwest tower is largely missing, having collapsed sometime in the 18th century.
The castle is entered via a short flight of wooden steps at the site of the original arched gateway, which also fell some time in the last 200 years. The grassy interior is dominated by the keep, the main residential structure. This has three stories, with the lower a basement; the entrance was on the first floor. On the south side is the remains of a full height turret, once containing a spiral staircase to access the upper two stories. Inside the southwest wall are three ground floor rooms of what was originally a two story range, probably used by servants. A window in one wall still contains its original 13th century iron frame. Other structures within the castle walls, including kitchens, were made entirely of timber and hence are no longer visible. There is one secondary entrance (the water gate) at the base of the northeast wall - steps and an archway, originally leading down to the moat, and now accessing the river. The corner towers have arrowslits but no windows, as they were used only for defence and storage; each contained a wooden staircase opening out to the upper turrets, which linked with a walkway all along the top of the curtain walls.
As is often the case, the first fortified structure at Skenfrith was a motte and bailey castle, constructed by the Normans soon after the 1066 conquest, and it was little changed for just over 100 years, when some additions were made, but the main construction happened between 1219 and 1223. At this time Skenfrith Castle along with the others at Grosmont and Llantilio Crossenny (White) was in control of Hubert de Burgh, later 1st Earl of Kent, who was one of the crown's most trusted barons, serving under kings John and Henry III. The Norman structure - part timber, part stone - was completely replaced with the castle seen today; an enclosing curtain wall with round corner towers, protecting the great keep. The work was carried out in two phases; the first attempt was ruined by floods, so the subsequent castle was started at a higher level, using river gravel piled on top of the earlier, unfinished building. The castle was briefly involved in countering Welsh insurgencies in the mid 13th century, though these subsided following the death of Llewellyn the Great in 1282, after which it was used only as a residence, by several Earls of Lancaster, a Plantagenet family. Although still occupied in the mid-15th century, the castle was abandoned soon after, and had become partly ruined by the mid 1500s, though a 1732 engraving shows it to be still mostly entire, with an intact northwest tower, a nearly complete entrance gate, and a water-filed moat around the perimeter.