This castle once belonged to a branch of the Mac Egans, a learned family who served as hereditary brehons, or traditional Irish judges, to the O'Connors of Connacht. The Mac Egans were part of Ireland's ancient learned class, preserving and interpreting Brehon Law for centuries before the English legal system took hold.

Today, the castle is very poorly preserved, with only the northeast corner standing at 2.4 metres high. The raised platform on which it was built measures 16 metres north to south and 10 metres east to west, rising 1.4 metres above the surrounding land. Whilst no architectural features remain visible at the site itself, one significant piece has survived elsewhere; a decorated and inscribed mantle stone from one of the castle's fireplaces now forms part of a wall at the National School in nearby Clonbern, preserving a tangible link to the castle's past grandeur.

Archaeological evidence suggests there may have been a bawn wall, a defensive structure typical of Irish tower houses, extending approximately 15.5 metres north from the castle's northeast corner. These fortified enclosures were essential for protecting livestock and providing a first line of defence during raids. Though Park Castle now exists mostly as earthworks and fragments, it remains an important piece of Galway's medieval landscape, marking the place where the Mac Egans once dispensed justice according to Ireland's ancient laws.