Construction of Castletown House began about 1722, for the Speaker of the Irish House of Commons, William Conolly. The son of a Donegal inn-keeper, Conolly was by then acknowledged to be the richest man in Ireland.
The facade of the main block was designed by the Italian architect Alessandro Galilei, and the house was built in the style of a 16th-century Italian town palace.
The work was supervised by Sir Edward Lovett Pearce, who was employed in 1724 to oversee the completion of the project. He added the colonnades linking the east and west pavilions to the main house.
Castletown remained unfinished at the time of William Conolly's death in 1729, although his widow continued to live there. The estate passed to his great-nephew, Tom Conolly, who recommenced work on the interior in 1758. During the following decades the style of the interior was influenced by the English architect Sir William Chambers.
The walls were decorated in the rococo stucco-work manner by the Swiss-Italian Lafranchini brothers. Tom Conolly and his wife, Lady Louisa, were responsible for much of the internal decoration of the house which survives.
Louisa spent vast amounts of her considerable fortune on it. She commissioned a dining-room ceiling based on the ceiling in the first-floor dining room in Leinster House, as well as much furniture, including giltwood tables, gilded mirrors and paintings.
Most notable is the print room - probably the only 18th-century one left intact in Ireland - which Louisa created. Here the walls are decorated in Louisa's favourite prints and decorative borders.
The Long Gallery, measuring almost 80 ft by 23 ft, was probably Louisa's favourite room and was used as a living room. The glass chandeliers were made in Venice and a statue of Diana stands in a central niche below a painting of Aurora, goddess of the dawn.
The obelisk, which is best viewed from the Long Gallery, was paid for by William Conolly's wife in 1740 as a relief scheme. Its design has been attributed to Richard Cassels.
It was built not on land belonging to Castletown or Lady Louisa, but belonging to the Earl of Kildare, apparently by mistake. It, too, is now in the care of the State.
