At the end of a two-mile straight line drawn from the garden front of Castletown House in County Kildare, a 140-foot tower of stacked arches, carved stone pineapples, and eagles on pedestals rises from the flat countryside. It serves no practical purpose, which is precisely the point. A folly, in the architectural sense, is a structure built for visual effect rather than function, typically to terminate a view or animate a landscape. This one does so on a scale that still surprises.

The structure was built around 1740 and attributed to the architect Richard Castle, who was among the most prolific designers working in Ireland at the time. It was commissioned by Katherine Conolly, widow of William Conolly, who had served as Speaker of the Irish House of Commons and accumulated one of the largest fortunes in the country. The folly was intended partly as a memorial to her late husband, but it also had a practical dimension: the construction provided paid relief work for local labourers during a particularly severe winter. The combination of dynastic display and social conscience embedded in a single eccentric monument gives it an unusual double character. The pineapple was, in eighteenth-century decorative language, a symbol of hospitality and wealth, expensive to grow and rarely seen outside the gardens of the very rich, which makes its repeated appearance here deliberate rather than whimsical. In 1989, Mariga Guinness, a founding member of the Irish Georgian Society and one of the key figures in the campaign to preserve Ireland's Georgian architecture, was buried beneath the central arch, adding a further layer to the structure's already layered history. The folly is now a National Monument in State ownership.