The castle and borough founded by Llywelyn ap Gruffudd in 1273 occupies the summit of a greatly scarped and terraced ridge. The original layout included two great towers, one round and the other rectangular, set in a rectangular walled enclosure about 70m north-east to south-west by 30m, with massive ditches cutting across the ridge. A third, D-plan tower projected from the long northern wall and there was a two storey domestic range between it and the round tower. The main entrance faced across the ditch to the south-west, approached by a massive ramp, roughly 50m long and 15m wide. The borough may have occupied the summit of the ridge beyond the ramp. A second entrance opened into a rock-cut ditch cutting the castle enclosure in two. It is possible that the intention was for two separate courts each with its own great tower, as appears to have been the case at Ewloe (NPRN 94447) and Criccieth (NPRN 95281).

The castle was unfinished in 1277 when it was besieged and captured by the English. The newly formed borough was removed and replaced by the foundation of Newtown (NPRN 33188). In the early fourteenth century the castle was adapted by Mortimer family with the addition of several new buildings, a hall, stores, a bakehouse and brewhouse. There was a grange or home farm outside the walls and building platforms beyond the great ramp may be associated with this, rather than with the earlier borough. By 1381 it was 'in a poor state of repair' and in 1398 it was 'ruinous and worth nothing'.

Between 1981 and 2002 the castle was cleared and excavated and its remains consolidated for public display.

Source: Butler & Knight CADW Guide to Montgomery & Dolforwyn castles (2004)

John Wiles, RCAHMW, 24 July 2007