On Kilmashogue Lane is St Columba's College, a Protestant boarding school. It was originally known as Hollypark and was built near the end of the eighteenth century by Gerald Foot, a wealthy snuff merchant. The school, which was founded in 1843 at Stackallen House, County Meath, moved there in 1849. In the chapel is an early Christian cross found on the mountain near the college. In his A History of the County of Dublin (1905), Francis Erlington Ball states that the barrier of The Pale ran along the northern slopes of Kilmashogue near the college and that the remains of a castle, held by the Harold clan who owned the lands for many years, could be found nearby. Opposite the college is the ruins of a woollen mill which was operated by Thomas Thorncliff until 1880.