The castle has had a rough time in the modern era, suffering significant collapses in 1905, 1963 and 1975, leaving only the northeast corner standing to its original four storeys. What remains reveals fascinating architectural details: a pointed vault running east to west over the second floor, though its southeast section has long since fallen away, and a clever system of mural stairs that wind through the eastern wall from the first floor doorway up to the third floor’s northeast corner.

The castle’s construction shows typical late medieval Irish defensive architecture, with thick walls containing a series of small chambers at the upper levels, visible through the broken sections of the eastern wall. The ground floor doorway in the east wall is now partially blocked with rubble from the various collapses, whilst there appears to be another entrance at first floor level in the same wall. A wide segmental arch spans the interior of the east wall, creating a recessed space that would have provided both structural support and additional room within the tower.

Local tradition attributes the castle’s construction to the O’Mahony clan around 1310, though the surviving stonework suggests a later date, probably from the 15th or 16th century. The O’Mahonys were one of the prominent Gaelic families of southwest Cork, and their castle at Rossbrin saw military action during the turbulent Tudor period; English forces attacked and captured it in both 1562 and 1571 during the Crown’s efforts to extend control over Munster’s Gaelic lordships.