The Wonderful Barn is a corkscrew-shaped building on the edge of Castletown House Estate of the Conolly family, which borders Leixlip and Celbridge, County Kildare, Ireland. It was built in 1743 on the Leixlip side of the Castletown Estate. Flanked by two smaller dovecote towers, it was built with the stairs ascending around the exterior of the building. Several purposes are suggested for the unique structure.