The castle once stood on lands that belonged to the Earl of Kildare in 1641, within the Parish of Conry, its strategic position on an east-west ridge offering surveillance over the surrounding pastures in all directions.

Today, only fragments of this once-imposing structure remain. A section of the south wall still stands, measuring about 3 metres east to west, 2 metres north to south, and reaching 5 metres in height. Traces of wall footings extend to the east and north, hinting at the castle's original footprint. Two substantial chunks of collapsed masonry lie about 5 metres west of the standing section, their medium-sized stones still bound together with rough mortar. The area shows signs of past quarrying activity, with uneven ground to the east and west, and loose stones scattered throughout the vicinity. A modern stone wall now runs parallel to the castle's remains, about 6 metres north of the ancient south wall.

Perhaps the most intriguing aspect of Carn Castle's history is a curious stone carving that once graced its walls. According to records from 1936, a sheela-na-gig, one of those enigmatic medieval female figures found on churches and castles throughout Ireland, was reportedly removed from the castle's fabric and came into the possession of a local man named Henry Upton. These mysterious carvings, often displaying exaggerated features, remain one of Irish medieval architecture's most debated elements, their true purpose and meaning still puzzling historians today.