The rectangular structure, measuring roughly 7.5 by 7.3 metres, tells the story of centuries of Irish landholding and displacement. The Siggins family held this land from at least 1342, when Thomas Siggin first appears in records, through to the Cromwellian confiscations of the 1650s. Edward Siggins, who owned 106 acres here in 1640, was marked for transplantation to Connaught in 1653; a fate shared by many Catholic landowners during this turbulent period. His estate passed to William Jacob, a Cambridgeshire soldier, whose family would occupy the castle for the next two centuries.

The tower house itself is a masterclass in medieval defensive architecture, though its builders clearly had comfort in mind as well. The original entrance on the north wall, now blocked, was once protected by a machicolation, portcullis, and murder hole; a formidable gauntlet for any unwelcome visitor. Inside, the ground floor chamber features an ingenious system of embrasures with double-splay loops and spy-holes that allowed defenders to observe approaches from multiple angles. These narrow openings, some extending over two metres through the thick walls, emerge as tiny apertures on the exterior, virtually invisible to attackers. The upper floors, accessed by a mural staircase, contained the living quarters complete with fireplaces, garderobe chambers with their chutes running down through the walls, and windows that once had internal shutters. Archaeological excavations in 2019 uncovered beaten clay floors at the second level and evidence of a hip-roof supported on corbels.

Sometime in the 17th or 18th century, the Jacobs added a two-storey brick house directly onto the north side of the medieval tower, creating doorways through the old stone walls to connect the two structures. This seven-bay brick façade represents a shift from defensive to domestic architecture, though recent excavations found only 19th-century material inside, including red-tiled floors and corner fireplaces. The combination of medieval tower and later house creates an unusual architectural timeline; one building growing from another across the centuries, each layer reflecting the changing fortunes and needs of its inhabitants.