Though the Siggins family held lands here from at least the 1550s, the castle itself doesn’t appear in records until 1641, when a Civil Survey noted that Philip Siggins had inherited the already ruined castle along with 300 acres at Sigginshaggard in Coolstuffe parish. The rectangular tower, measuring roughly 6.6 by 6.1 metres externally, rises nearly 11 metres high through five storeys, its battered walls still reaching almost to where the wall walk once ran.

The defensive features of Siginshaggard reveal the paranoia of its age; no fewer than twenty gun-loops and spy-holes pierce its walls, allowing defenders to monitor and fire upon approaches from every angle. Entry was through a pointed granite doorway on the southwest wall, originally protected by an iron yett (gate), machicolation above, and what appears to have been a murder hole operated from the first floor. Inside, the tower’s layout follows typical Irish tower house design, with a ground floor chamber lit by double-splayed loops, a vaulted first floor featuring wicker-centring impressions still visible in the barrel vault, and upper floors that once held the main living quarters, complete with fireplace, garderobe, and windows offering slightly more comfort than the fortress-like lower levels.

The tower stands at the eastern corner of a square, grass-covered bawn measuring 28 by 28 metres, its boundaries still traceable as a slight bank with an outer fosse about 9 metres wide. Though time has taken its toll on the battlements and upper stairs, and many of the doorways between floors have collapsed, Siginshaggard remains an evocative reminder of the uncertain times when even minor gentry needed homes that could withstand a siege. The progression from defensive ground floor to progressively more domestic upper storeys tells the story of 16th-century Irish life; perpetually balanced between the needs of daily comfort and military preparedness.