Oystermouth Castle sits on top of a small hill near the Mumbles headland, overlooking Swansea Bay at the southeast corner of the Gower Peninsula; once an isolated, rural location, the fortress prominently visible across the surroundings, but now the site is rather hidden, obscured by modern development and growth of trees. The castle has a long history, beginning around 1106 soon after the conquest of Gower by the Normans, and although very little remains from this period, the structure was added to at various times over the next 200 years and occupied until the 1400s, after which it became ruinous, however what remains is substantial, one of the premier historic attractions of Swansea, all the more so after a major restoration in 2010-2011.
The castle has an approximately oval outline with a gatehouse at the south end, leading to an enclosed courtyard, on the far side of which are four connected ranges, most impressive being the three-storey chapel block, illuminated by elegant, traceried windows, looking out across the bay. Unlike most medieval castles in Wales the place is not managed by Cadw but rather by the local council, who charge a reasonable fee for admission. Around a dozen rooms can be toured, on several levels, plus a section of wall walk. Free parking is available on narrow streets to the south, and the castle is open between April and September. The name Oystermouth, a translation of the Welsh ystum llwynarth, is thought to be a reference to the ancient practice of cultivating oysters in the bay.
The first castle at the site was established by William de Londres, Lord of Ogmore, and was probably an all-timber fortification, which survived only a few decades, being mostly or completely destroyed during a Welsh incursion of 1136, though it was recaptured and rebuilt shortly afterwards. The first definite mention in historical records is 1215, when the castle was once again briefly taken by the Welsh, approximately same time as the death of Thomas de Londres, the last of that family to reside here. Gower was occupied for a few years but then returned to full English control in 1220, after which the castle passed to the de Braose family, who began a major reconstruction, mostly under William de Braose (died 1291). The family resided here only until the 1330s, after which the place was maintained and regularly visited for another hundred years or so, then became gradually abandoned and was left to decay. In the earliest known illustration, 1751, the castle is not much different to its current appearance.
The earliest castle, post the 1136 rebuild, is thought to have consisted of a stone keep at the centre, atop a natural limestone outcrop, surrounded by timber defences. The keep was repaired upon recapture of the Gower in 1220, and augmented by a addition of a three story tower on the north side, creating an imposing, square-shaped block, completed around 1232. This was further expanded a few decades later by addition of a tower to the northeast, containing two stories above a basement, plus an initially unconnected room to the west, while the next stage, maybe 30 years later, involved building a curtain wall all around to the south, enclosing a courtyard, with a gatehouse on the far side, and also the connection of the detached west block via another room, linking with the northwest tower. The last major additions were at the start of the 14th century, principally the chapel block on the east side of the original keep, a building associated with Aline de Braose, daughter of the last Lord, and wife of John de Mowbray. Also around this time two single-floor ranges were erected inside the south curtain wall, either side of the gatehouse, plus a two-storey porch on the south side of the central block, providing a grander entrance to the main hall. All the residential areas were equipped with fireplaces, garderobes and arched windows, and offered a high standard of comfort.
The approach path leads up quite a steep slope to the two-storey gatehouse, which was originally flanked by two round towers, long since removed, though their position is evident from the concave walling at either side of the frontage, and the gated doorways at the base, once accessing the tower staircases. Visitors enter through a barrel-vaulted passageway, on the far side of which are two flights of stairs that access the upper level of the gatehouse, a now roofless room, linking to wall walks to the east and west. The main section of the castle, the four connected ranges, is on the far side of the courtyard, and the most impressive is the 14th century chapel block. This had a ground floor basement (now housing the gift shop and fee station) and a first floor apartment, with the high-ceilinged chapel above. The intermediate floors are missing, replaced now with a modern walkway, partly of glass, which allows close inspection of the chapel; features include five decorative windows (partly restored in 1845), a buttressed chimney column, several recesses, and the fragmentary remains of a medieval wall painting. The northwest corner of the chapel abuts the central block, incorporating part of the early Norman keep, where rooms included the dining hall and kitchen. A narrow spiral staircase on the west side rises to a viewpoint of the upper floors, and connects with a ground level passageway that links to the northwest tower, which has a basement, entered via a separate stairwell. The other major component is the west range, which consists of two adjacent rooms, each above vaulted basements.