The Wonderful Barn, Leixlip, was built by the widow of Speaker Connolly, Laura Catherine Connolly, in 1743. Primarily, it was built in order to provide employment for the poor. Secondly, to store grain from the O'Byrnes and O'Tooles who would come down from the Wicklow hills to steal and forage for food.
The barn is conical in shape and rises some seven floors. The grain was hauled up through a circular hole in the centre of each floor. It was then spread out on these floors to dry and was later packed into sacks for winter storage. A flight of ninety four steps winds round the exterior of the structure.