Built by the Purcell family in the 15th century, the castle takes its name from the earlier De la Frene owners, among whom Fulk was a common Christian name. The tower house measures 11.5 metres north to south and 9.4 metres east to west, constructed from roughly coursed limestone rubble with carefully cut stone corners. Its defensive features remain impressive: a significant base batter rises about 4 metres high, whilst the parapet sports crow-stepped crenellations with mural chambers along the north and south walls. The original entrance, now obscured by a later building, leads through a pointed doorway complete with yett-holes into a double lobby protected by both a murder-hole and cross-loop, with a guardroom positioned strategically to the east.

The castle’s tumultuous history reflects Ireland’s changing fortunes over the centuries. Following the 1641 Rising, Cromwell seized the property from Philip Purcell, an Irish Catholic, and granted it to Christopher Mathews, Theophilus Eaton, and Joseph Bradshaw. The Down Survey maps of 1655-6 record it as ‘a castle in repaire’ with some cabins nearby. By the mid-18th century, ownership had passed through the Grene family to the Wrights, and subsequently to the Ryans. Thomas Wright’s fifth son Stephen undertook significant restoration work in the late 18th or early 19th century, enlarging windows, adding panelling and plasterwork, and reducing the size of the massive fireplaces; one original hearth reportedly stretched an impressive 17 feet across.

The interior preserves a fascinating blend of medieval and later features. A spiral staircase in the northwest angle provides access to all upper floors, which retain wooden flooring except for the third floor’s vaulted roof. Original single-light windows with flat, round, and ogee-headed designs illuminate the lower levels, whilst elegant ogee-headed two-light windows with hollow spandrels grace the fourth floor. The 18th and 19th-century renovations added flat or elliptical-headed windows with hood-mouldings that cleverly mimic early 17th-century style. Garderobe chambers built into the east and south walls at the third and fourth floors remind visitors of medieval practicalities. After serving as an An Óige youth hostel from 1947 to 2009, complete with metal fire escape balconies, the castle has returned to private ownership, continuing its long story as one of Kilkenny’s most enduring fortified residences.