Adjacent to the stairhall, this room is part of the 18th-century building and was probably used originally as a dining-room. It retains much of its authentic character, with vigorously shouldered wall-panelling, similar to that in the inner hall and splendid door-cases. However, the door to the left of the chimney-breast, leading to the extension added by Benjamin Lee Guinness, dates from 1866 and so do the windows.
The chimney-piece is partly original. Its frieze is another example of the fine 18th-century woodcarving seen in the house. It has a charming and delicate motif of putti making wine and a centrepiece representing the drunken Silenus, copied by its carver from an engraving of a Rubens painting. This is probably the frieze of the room's original chimney-piece for its theme is suited to a dining-room, but it has been shortened, and incorporated into a rather coarse neo-Georgian fire surround, probably by J F Fuller circa 1880.
The most beautiful feature of the room is its ornamental plaster frieze. Like other decorative plasterwork at Iveagh House, this would seem to post-date the construction of Bishop Clayton's house in 1736, for its naturalistic precision has little in common with the more generalized Baroque style of plasterwork in other Richard Castle houses. It seems logical that it is late roccoco work, installed after Viscount Mountcashel bought the house in 1766. To instal fashionable new plasterwork decorations was a means of up-dating an existing building and is something which apparently happened frequently in Irish 18th-century houses of both town and country.
The frieze is extremely delicately modelled, and each wall of the room is treated differently.Among the motifs are roses, tulips, swags of laurel leaves, shells, and, in three of the four corners, bunches of grapes, again suggesting a former use as a dining-room.