Recognised as a strategically important location since Roman times, Tretower Castle was the predecessor to Tretower Court, significantly demonstrating the change from castle stronghold to comfortable, domestic residence, as the needs of war and peace dictated.

Probably constructed of earth and timber, Tretower Castle was typical of the many motte and bailey castles built at the time of the Norman Conquest of South Wales. In the mid-12th century a shell Keep and Gatehouse were constructed on the 'motte' (or mound), and within the Keep an L-shaped block contained the Hall and Solar. This ruinous building displays some of the finest Romanesque domestic work to survive in Wales and, although well weathered, the windows especially show some splendidly carved detail.

During the first half of the 13th century, the Great Tower (round Keep) was built inside the original shell Keep, stone curtain walls with round towers replaced the wooden fences. These circular Keeps were quite common at this time, the design being copied from similar towers seen in France during campaigns. Constructed with three storeys and a basement, the Great Tower could adequately protect Tretower Castle, and a bridge was built between the tower and the curtain wall providing means of communication. Except for the top section, this Great Tower has remained virtually intact, as well as a small section of the parapeted wall-walk.

At some time during the early 14th century, a four-storey building between the tower and the shell Keep was added, although the purpose of this is unclear. One theory is that it provided accommodation and storerooms for the garrison occupying Tretower Castle during troubled times when, perhaps, the main part of the castle had deteriorated. However, the earliest work on Tretower Court has been dated to c1300, when Tretower Castle's occupants probably decided to take up a more comfortable residence. Despite the original building being gutted during the 15th century uprisings, and many alterations and modernisation work carried out over the following 200 years, a significant amount of 14th century evidence can still be seen, notably in the north range.

Together, this substantial fortified manor house and the ruins of Tretower Castle illustrate quite clearly the changing times and fortunes of medieval life. Situated in a very picturesque valley, beneath the shadow of the Black Mountains, this is an extremely fascinating and evocative site.