Though the castle itself has vanished completely, with not a single stone left standing since around 1800, it likely stood within a large square enclosure that appears on 19th-century Ordnance Survey maps. The site offers decent views to the northwest, north and northeast, but the outlook is otherwise poor. Intriguingly, whilst the castle doesn't appear on either the 1839 or 1900 OS maps, it is clearly marked on the earlier Down Survey maps from 1655-6, suggesting its destruction occurred sometime between these periods.

The Grace family's connection to this area stretches back to the mid-13th century, when William le Gras traded his Gloucestershire estates for Irish lands including Tullaroan in 1283. By 1470, Baron Oliver Grace of Tullaroan was serving as Keeper of the Peace in County Kilkenny, and his descendants continued to hold the estate until their downfall following the Williamite wars. Robert Grace of Courtstown was outlawed and died from wounds sustained at the Battle of Aughrim in 1691; his eldest son Oliver died just nine days later whilst in France. Through a quirk of inheritance law and a malicious court case in 1701, the family lost their ancestral home, which was sold to the rather unusually named Company for Making Hollow Sword Blades. The new owners promptly stripped the lead from the roof, beginning the castle's decline.

An elaborate description of the castle published by Mason in 1819 paints a picture of a grand fortification with round towers at each corner, a massive keep, portcullis, inner and outer courts, and even a bowling green and cockpit. However, this account, along with several contemporary illustrations, is now suspected to be largely fictional, likely commissioned by Sheffield Grace between 1788 and 1850 to enhance his family's reputation. What we do know is that by 1800, the castle had been so thoroughly plundered for building materials that its very foundations were being dug up. Today, visitors to the site will find only marshy ground where this once-mighty stronghold stood, a testament to how completely even the grandest buildings can disappear when abandoned to time and opportunistic neighbours in need of stone.