Carmarthen castle originates from the beginning of the 12th century and replaced an earlier fortification located further down the River Towy. Later passing into the hands of the Crown and becoming the administrative centre of south west Wales. Captured and destroyed by Llywelyn the Great in 1215 it was recaptured by William Marshall the younger, earl of Pembroke in 1223 – the first masonry castle may have been constructed at this date.
The remains of Carmarthen Castle comprises a stone-revetted motte, twin-towered gatehouse, a south west corner tower and wall turret east of this together with short sections of curtain wall, all to the west of the site. The motte walls have two small half-round turrets to the north and paired buttresses representing the site of a further turret to west, the majority of this fabric is the result of 19th century reconstruction.
The monument is of national importance for its potential to enhance our knowledge of medieval defensive practices. The monument is well-preserved and an important relic of the medieval landscape. It retains significant archaeological potential, with a strong probability of the presence of both structural evidence and intact associated deposits.