Built by the Plunkett family from coursed limestone blocks with carefully dressed stone quoins, this National Monument showcases the defensive architecture typical of medieval Ireland. The entrance, through a three-centred arched doorway on the north wall, leads into a barrel-vaulted main chamber that still displays evidence of its original wicker-work centring; a fascinating glimpse into medieval construction techniques.

The castle's interior reveals a complex arrangement of chambers and defensive features across its multiple levels. Three of the four corner turrets contain chambers, whilst the northeast tower houses the main staircase. The ground floor chambers, lit only by narrow defensive slits, include vaulted spaces in the northwest and southeast towers. As you ascend, the first floor opens up with taller rectangular windows and contains intriguing domestic features: a brick fireplace with chamfered jambs in the northwest tower, a garderobe and wall press in the southwest, and a curious hollowed basin with drainage in the southeast tower, alongside strategically placed musket holes for defence.

The upper floors retain remarkable original features, including substantial roof timbers above the third floor and a fireplace with flat arch and chamfered jambs on the west wall. The corner chambers feature corbelled roofs topped with Tudor-style chimneys, whilst battlements accessed through a pointed arch in the northeast tower complete the defensive arrangement. Archaeological surveys of the surrounding lands have revealed evidence of historical agricultural activity, including possible ridge and furrow cultivation patterns that may date to the castle's active period, painting a picture of Dunsoghly not just as a defensive structure but as the centre of a working medieval estate.