The ruins of Castell y Bere do not rise to any great height, but they do clearly show the layout of the castle, built on a rocky outcrop in the Dysynni valley. Its isolated location in a beautiful setting makes it worth visiting for the scenery alone.

The castle was built by Llywelyn the Great in the 1220's, and guarded what was once a major route though the mountains. In 1283 the castle fell to the forces of Edward I, led by Robert l'Estrange and William de Valence. The castle was refortified by the English and held until 1294 when it was attacked during a Welsh revolt led by Madog ap Llywelyn. The castle was badly damaged and subsequently abandoned.

The layout of the castle is dictated by the shape of the rock peninsular on which it is built. The defensive properties of the rock were enhanced by the addition of rock-cut ditches. At the north and south ends of the castle are two typically Welsh D-shaped towers. Remains excavated from these two towers suggest that both offered a high level of accommodation and that the north tower contained a chapel on the first floor. There is a third rectangular tower at the highest point of the castle that would have served as a keep. The main entrance was unusually well defended for a native Welsh castle and was flanked by the rectangular keep on one side and a round tower on the other.