The remains of this castle, begun by Llywelyn ap Gruffudd ('the Last') in 1273 and captured by the English in 1277, have been revealed by excavations.
Dolforwyn Castle was built between 1273-77 by Llywelyn ap Gruffudd (Llywelyn the Last) as a forward position in his territory, and overlooking the English lordship of Montgomery.
This rectangular castle crowns a ridge along the Severn valley, and was obviously designed to act as a sentinel over Llywelyn's south-eastern frontier. Its initial construction led King Edward I to write to Prince Llywelyn in 1273, forbidding him to build the castle. The prince replied, with a masterpiece of ironic politeness, that he did not require the king's permission to raise a stronghold in his own principality.
Dolforwyn was, however, taken by Roger Mortimer after a fortnight's siege in 1277, and given to the Mortimers, a powerful marcher family. The castle was kept in repair for some years, but was ruinous by 1398.