With their elaborate decoration, the labour of Europe's top painters and plasterers, they were the designer rooms of their day.
But more than 200 years after their careful creation the ancient plaster ceilings in the magnificent state dining room and tapestry drawing room at Inveraray Castle are being prepared for repair.
The Duke of Argyll has applied to Argyll and Bute Council for listed building consent to carry out the work at his ancestral home this winter.
The plasterwork in the state dining room was carried out in 1781 and 1782, its ceiling was adorned with decoration cast in London by John Papworth, while its cornice and frieze are the work of renowned Scottish plasterer John Clayton.
The elaborate painted decoration of the room, which was completed in 1784, is the only surviving work of the French painters Girard and Guinard, who were also commissioned by the then Prince of Wales, later George IV, to decorate his London residence, Carlton House.
Decorated in the Parisian style of the 1780s, the tapestry drawing room also boasts architectural decoration by Girard, while its original ceiling was designed by Robert Adam and gilded by Dupasquier.
Argyll Estates factor Andrew Montgomery said: “It has all been discussed with Historic Scotland. We are doing some refurbishment in the castle and we have come across some parts of the ceiling which need screwing back up."
The castle itself is an architectural gem, incorporating baroque, palladian and Gothic influences. Design work began in 1720, with a sketch which was prepared by Sir John Vanbrugh, the architect of Blenheim Palace and Castle Howard, for the 2nd Duke of Argyll. Construction started in 1746, after Vanbrugh's death, and the design was developed by Roger Morris, who worked with William Adam, then the most prominent architect in Scotland.