15th Century Ross Castle is located 1.5 km from the Town Centre on Lough Leane. There are few castles anywhere in Ireland that can boast such a dream-like enchanted setting as this ruined tower house on the shore of Killarney's Lower Lake. Built in the late fifteenth century, it is fairly typical of its type, with square bartizans on diagonally opposite corners and a thick end wall containing a tier of chambers and a winding mural stair.

The tower stands within a square bawn defended by round corner towers, two of which survive, the others having been removed in 1688 to make room for an extension, the ruins of which remain on the south side of the castle.

The castle was the chief seat of the O'Donaghue Mors, hereditary rulers of this district and descendants of the ancient kings of Munster. After the Desmond rebellion their fortified lands were acquired by the MacCarthy Mors from whom they were purchased by Sir Valentine Browne, ancestor of the Earls of Kenmare.