Usk Castle is a substantial masonry castle dating from around 1138 and now generally ruinous. It is first recorded in the possession of Richard de Clare in 1262, but probably held by the de Clare family from the conquest of South Wales. It subsequently passed through severeal hands in the fourteenth century and for a time was controlled by Edmund Mortimer, Earl of the Marches. After the death of his nephew Richard, the Duke of York, it passed to Edward VI, subsequently staying in the hands of the crown until the death of Henry VII. It then passed to the Earls of Pembroke.

The castle stands on a spur overlooking the Usk and consists of a rectangular area surrounded by curtain walls with towers at intervals and a large gatehouse on the east side. To the south-east is an outer bailey with walls on its south-east side, a corner tower on the south, and a gatehouse at the north end of the south-east wall.

The gatehouse is square in plan, a three storey structure with a doorway reached by stone steps on the east side and round headed windows on the south side. Internally there is a fireplace on the north-west side, and a number of doorways at different levels.
The north tower is D-shaped with a large square-headed doorway with a square mullioned window above on the inside wall, and external doorways in the north and south walls, that to the south leading to a small platform. On the first floor is a fireplace.
The banqueting hall is 14th century in date, being altered around 1500. It stands against the curtain wall on the north side. Along its south side is a buttressed wall with two windows and a doorway, with a third window above. The west wall has a further, large window and there is a fireplace in the north wall at first floor level. The Garrison Tower is circular and located midway along the south-west curtain wall. It stands to its full height with a crenallated parapet, and there are doors into it on either side of the curtain wall. At a level corresponding to the top of the curtain wall is a small passageway leading to a garderobe on the north side and a spiral staircase on the south side, and there are small slit windows on four levels.

The Round Tower in the south corner, stands to the same height as the curtain wall, with a doorway surviving on the north side.
Curtain walls survive to various heights. On the north-east side there is a large gateway with a pointed arch, to the west of which is a low grass bank. Above this are three supports in the wall for the first floor of the building that was there. There is also a tapering fireplace in the middle. To the north of the gateway is another fireplace and grass covered low remains of rooms, and to the north of this is a small projection with a rounded niche. The north side has St Georges chapel, an area of garden made into an open air chapel. At the west end a small tower projects to the outside of the curtain wall, internally having a fireplace and the remains of a spiral staircase. The south-west curtain wall retains its wall walk, and there are three openings, one of which has a pillar and appears more recent. The south-east wall has a small 'room' inside the wall at an upper level.
The Dovecot tower is at the south end of the outer bailey wall; it is round in plan and stands to its full height. The internal north-west wall has niches for use as dove boxes.
(Source SAM description)

S Fielding, RCAHMW, 20 June 2005