This was the great room so much admired by Lord Orrery in 1736. In Bishop Clayton's day it was a saloon - a formal drawing-room - and its original function is matched by the architectural grandeur of its decorations. Today it remains largely as Richard Castle designed it.
The Iveagh House saloon was the prototype for two of the finest rooms in Irish architectural history - the saloons at No. 85 St Stephen's Green and Carton. Co Kildare. Both probably date from the same year, 1739, and are decorated with magnificent Baroque plasterwork by the Francini brothers. By contrast the Iveagh House saloon of 1736, which probably pre-dates the arrival of the Francini brothers in Ireland is decorated with a classical restraint which is close to the manner of some English Palladian architects - notably William Kent whose saloon at No 44 Berkeley Square, London (1745), parallels Bishop Clayton's.
In decorating the deep cove of the saloon ceiling, Richard Castle used square, cross- shaped and octagonal coffers modelled in perspective adapted from a plate in one of his favourite works of reference, Serlio's Five Books of Architecture, showing the coffering of the Temple of Bacchus in Rome. On the east wall of the room are two semi-circular coffered niches. It seems that, as at No 85 St Stephen's Green, there were two more niches on the opposite wall which presumably were filled in during the 1866 remodelling.
Probably the original arrangement in the two houses was to have a fireplace on both end walls of the saloon flanked on either side by niches. Also identical to the arrangement at No 85 is the pairing of the doors on the inside wall of the saloon, one door opening into the adjoining old music-room. the other opening on to the landing. This skilful arrangement enables the first-floor reception rooms to interconnect while preserving the symmetry of the saloon.
The saloon doors are of mahogany to the same design as in the old music-room and the mahogany dado is also original. The rest of the woodwork is Victorian, the windows dating from 1866 and the fireplace from 1880.