The elegant Georgian house that stands today, built around 1785, is a five-bay, two-storey structure over a basement, but it's what came before that truly intrigues. Historical records from the 1654 Civil Survey describe 'an old demolished castle, the walls onely standing without any other Improvement' at Rathinan, and many believe South Park was constructed on these very foundations.

The mystery deepens when examining the cartographic evidence. Strafford's 1637 survey shows both a castle and dwelling at this location, whilst the Down Survey map from 1654-7 depicts the castle of Rathinane standing just north of a turlough, those seasonal lakes characteristic of Irish limestone landscapes. The current house sits roughly where these old maps suggest, though some historians argue the medieval castle may have occupied a slightly different spot. What is certain is that the three-storey block attached to the rear of the Georgian house predates the 18th-century construction and may well incorporate remnants of the medieval stronghold.

Today, South Park presents itself as a refined country house with its artificial slate roof, rendered walls, and cut stone cornice, offering sweeping views across pastureland from east to west. The National Inventory of Architectural Heritage notes the building's architectural details; the hipped roof on the front block, the large square stone chimney stack on the older section, and the tie bars that hint at structural repairs over the centuries. Whilst no castle ruins are visible at ground level, the site continues to tantalise those interested in Ireland's medieval past, where Georgian elegance literally builds upon the foundations of earlier fortifications.