This imposing ruined structure is located close to the summit of Mountpelier Hill in the Dublin Mountains, facing north east across the low-lying areas of Tallaght and Rathfarnham. It was built in 1729 by the Right Hon. William Connolly, Speaker of the House of Commons. It is thought that a nearby cairn which had dominated the summit was demolished to build the house and that stone from the ancient structure was used in the construction of the building, fueling the beginning of the site’s long established reputation in the realm of the supernatural. Local stories abound of the notorious activities of young, and not so young, men of the 18th Century cult - The Hell Fire Club - engaged in satanic and debaucherous activities in the house. The house itself consisted of two large rooms and a hall on the upper floor with the ground level being occupied by the kitchen, servants’ quarters, and a stairs to the upper level. On the outside, a lofty flight of steps led to the hall door. When the roof was blown off in a great storm, Connolly replaced it with a great arched room of stones set edgeways and infilled with smaller stones and mortar. This impressive roof still stands today though the rest of the house is in a ruined state.