This is Conolly’s Folly, found here on a map. It’s found on the road to Celbridge, on the right of the aptly named Obelisk Lane.
It’s a unique structure, nothing like its kind is found elsewhere in Ireland. Built between 1739 – 1740, commissioned by Catherine Conolly (Lady Conolly), who lived at the local Castletown House estate. It was apparently built as a famine relief project due to a severe famine the previous winter. It closes the view at the back of Castletown house. It’s a stone structure 140 feet in height. It was designed by architect Richard Cassels, who designed Carton House and Leinster House. It cost £400 to build. Workers were paid half a penny a day and local stories say that the stone was transported from a quarry in Leixlip along a human chain all the way to the site! It turns out the land on which it was built was not owned by the Conolly’s, but by the Earl of Kildare, the owners of Carton House! (hence the name ‘Folly’).
A History of Co. Kildare by Padraic O’ Farrell,
Maynooth (Má Nuad) by Mary Cullen, 1979
Exploring Maynooth: Five Self-Guide Historical Walks by Mary Cullen et al.