This small rectangular tower, measuring just 6.1 metres north to south and 7.6 metres east to west, rises four storeys despite centuries of neglect and modification. The castle sits on level ground that formerly belonged to the demesne of Little Island House, itself now reduced to rubble after being abandoned; the house was once a substantial late eighteenth-century residence, possibly designed by Davis Duckart and home to the Bury family.

The tower’s architecture reveals its defensive past through a complex arrangement of entrances and internal passages. A reconstructed ground floor door near the western end of the north wall features a segmental vault over its passage, whilst upper floors were accessed through separate entrances; a first-floor door sits centrally in the south wall, and a second-floor entrance near the eastern end is flanked by external corbels that once supported wooden fore-stairs. This second-floor doorway leads directly to an internal chamber and connects to a stairway built into the eastern wall, which rises to the third floor. The interior preserves several original features including narrow, splayed windows for defence and light, and remarkably, a pointed vault with wicker centering that still covers the second floor.

Despite its local name, the castle has no confirmed connection to the Wallyns or Waleys family, later known as Walsh. Historical records indicate the Fitzgeralds held the castle during the sixteenth century, though it formed part of the larger Barrymore estate. The upper portions of the structure show evidence of later modifications; the walls above the vault have been reduced to form gables for a more recent roof that has since disappeared, and a wide central opening in the south gable appears to be a relatively modern addition. Archaeological excavations in 2003 have added to our understanding of this modest but intriguing fortification, which stands as a testament to medieval life in County Cork.