Castell y Bere was established by Llywelyn ab Iorwerth in 1221 on land seized from his son, Gruffudd. It was intended to secure Llywelyn's lordship and protect the southern periphery of his territory.

Extensive masonry ruins remain of the castle complex, which as well as rectangular and round towers includes two characteristically Welsh elongated D-shape towers, the southernmost of which differs from typical design, being isolated from the main castle structure, overlooked by the rectangular keep, and accessible from the ground floor, thus rendering it defensively weak. The castle had a highly elaborate defended entrance with ditches and two gate-towers, each with a drawbridge and portcullis.
Bere was surrendered to Edward I in April 1283, following the defeat of Llywelyn ap Grufudd the previous year. The castle was further fortified with the thick walls linking the south and middle towers, and a small borough was established. Neither the castle nor the borough remained in use after the 1294-5 Welsh uprising, however, during which Madog ap Llywelyn unsuccessfully attempted to re-take the castle for his family. The English abandoned the site and it disappeared from the historical record until the ruins were cleared in 1851 when Roman pottery and coins were recovered from the fabric of the well.

Sources include:
Avent, R. 2004. Dolwyddelan Castle, Dolbadarn Castle & Castell y Bere: Cadw Guide

K Steele, RCAHMW, 4 November 2008