This castle is situated in the parish of Straffan, County Kildare, in the barony of North Salt, about a mile north of the village of Straffan.
The name is spelt variously Barberstowne, Barbeston, Barbieston, Barbiestowne, Barbiston, Barbitstowne, Barbyeston.
The present building consists of a battlemented rectangular keep considered by experts to be of thirteenth-century construction, and measuring at its greatest height 52 feet. It is divided into three floors. The lower room, which is vaulted to the height of 17 feet, is 18 feet long by 15½ feet wide, and the walls are 4½ feet in thickness.
The entrance is situated at the north-west angle, above which are two grooves of sufficient width to stand in, and evidently intended for the protection of the doorway.
The room above the vault is of slightly greater proportions than that below, owing to the walls being of less thickness.
Two small rectangular towers are joined to the main building on the south side’s western angle, and west side’s northern angle respectively. The latter contains a winding stone stair of fifty-three steps leading to the now slated roof. The original crenelated loops for musketry have here and there been enlarged to admit more light. The summit of the watch tower is reached from the roof by a short flight of nine steps.
A man is said to be interred between the top of the main stair and the roof of the tower. His family having held the castle by a lease which expired when he was put underground, determined to evade relinquishing their hold on the property by keeping him always above the earth.
The southern tower consists of three storeys corresponding with those in the keep, and had formerly doors opening from the main rooms. Next the southern wall is a curious slit in each floor just wide enough to permit of a ladder giving access to the apartment above or below. The ground floor in this tower is of very small dimensions, being about 3 feet square.
The walls of the keep slope considerably at the outside base so as to prevent an enemy getting out of gun shot by closing up to the building. Large modern windows now light each floor, and the whole is in excellent preservation.
A flue runs in the thickness of the wall on the north side, which is crowned by a handsome brick chimney, evidently added when the Elizabethan dwelling-house which adjoins the castle was erected. A still more modern house has been added to the north of this building, so that at present three distinct periods are represented by the castle and houses, which are all joined together.