The folly was built within Castletown Estate (containing Castletown House), which contains two follies, both commissioned by Katherine Conolly, the philanthropic widow of Speaker William Conolly, to provide employment for hundreds of the poor of Celbridge when the famine of 1740-41 was at its worst. The Obelisk was built in 1740 after a particularly severe winter. As a folly, it could be seen from the back of Castletown some 2.5 miles away and it is built exactly perpendicular to the house. It was intended to mark the rear entrance gateway to Castletown house in conjunction with an avenue leading to the house.
Designed by Richard Castle, it is 42 metres (140 feet) high and is composed of several arches, adorned by stone pineapples and eagles, topped by a massive obelisk pillar. It was restored in 1965 by the Irish Georgian Society, and nearby is the grave of Mariga, first wife of the Hon. Desmond Guinness of Leixlip Castle.
- The Wonderful Barn
- Nearby towns of: Maynooth, Leixlip and Celbridge
- Kildare History and Society 2006 ed. Nolan W. & McGrath T., at pp. 327–348. ISBN 978-0-906602-57-7
- Paintings of the Obelisk
- Fantastic Follies (Photos of well known Irish Follies)
- Description of the Obelisk
- Tourist Guide, with Description of Connolly's Folly