Iveagh House was originally two houses, nos 80 and 81 St Stephen's Green. No. 80 was designed by Richard Cassels in 1736 for Bishop Clayton. It was later the home of barrister and Master of the Rolls John Philpot Curran.
After both houses were bought by Benjamin Guinness in 1862 he served as his own architect, combined the two houses and produced the building as it now stands. On the Portland stone facade pediment he placed his parents' arms: on the left the Milesian lion, with the red hand of Ulster above, for the Magennis clan of County Down; and on the right the arms of the Lee family, Dublin builders from about 1700. The building has nine bays, with the central three broken forward and pedimented. The interior of the building is hugely elaborate and decorative, with a staircase and ballroom lined with alabaster. The staircase also has ornate ironwork, marble columns and circular roof lights.
The Iveagh Gardens at the back of the house were given to University College Dublin by Lord Iveagh in 1908, in connection with the formation of its campus on Earlsfort Terrace. The gardens have since been transferred to the OPW and are now used as a public park.