Built on the site of a 7th-century monastery founded by Saint Carthage, the castle has witnessed centuries of Irish history unfold beneath its battlements. The current structure dates largely from the 19th century, when the 6th Duke of Devonshire transformed what remained of a medieval fortress into a Gothic Revival masterpiece; though its foundations incorporate elements from the original episcopal palace that once housed powerful bishops and served as a centre of learning in medieval Ireland.

The castle’s history reads like a chronicle of Ireland’s most turbulent periods. After the dissolution of the monasteries, it passed through the hands of Sir Walter Raleigh, who reportedly planted Ireland’s first potato crop in its gardens, before being acquired by Richard Boyle, the 1st Earl of Cork, in 1602. The Boyles transformed Lismore into one of the most magnificent estates in Ireland, only to see it severely damaged during the Confederate Wars of the 1640s. When Lady Charlotte Boyle married the 4th Duke of Devonshire in 1753, the castle passed to the Cavendish family, who maintain ownership to this day.

Today’s visitors can explore the castle’s spectacular gardens, which span seven acres and include both formal and informal sections. The upper garden, dating from about 1850, features ancient yew walks and modern sculptures, whilst the lower garden hosts a remarkable collection of contemporary art alongside traditional herbaceous borders. Though the castle itself remains a private residence, occasionally hosting notable guests including members of the royal family, its gardens open to the public from March to September, offering glimpses of both horticultural excellence and the layered history of this remarkable estate where monks once prayed, poets found inspiration, and dukes built their dreams in stone.