The main door of the entrance hall leads into the principal interior feature of Morrison's house - a great central hall with an octagonal balustraded gallery lit from above, through a dome filled with stained glass.
The Central Hall
The room now features pieces of sculpture, as it was probably originally intended to, and display cabinets contain a striking Chinese export armorial service with the arms of Sir Robert Cowan, Governor of Bombay, whose fortune provided the Stewarts with the means to acquire the house in 1744.
In mid Victorian times however, the fourth Marquess (1805-72) filled the hall with over 3,000 antlers, a wide variety of animal heads, heraldic banners and suits of armour.
A passage from the central hall leads to the core of Dance's earlier house and an imperial staircase with stone treads, wrought-iron balusters and a ramped mahogany handrail. The roof has an octagonal skylight dome with segmental arch supports that is typical of Dance and of his famous pupil Sir John Soane.
The dominant feature of the room, and perhaps the most important picture in lreland, is the magnificent 'Hambletonian', the masterpiece by George Stubbs. It depicts a racehorse owned by Sir Henry Vane-Tempest being rubbed down after it had just beaten Joseph Cookson's horse, Diamond, at Newmarket in 1799.
The Music and Castlereagh rooms
Adjacent to the staircase hall is the music room, which lies at the centre of the west front, flanked by the sitting-room and the Castlereagh room. All three rooms remain very much as Dance had left them, particularly the music room with its delicate ceiling of pendentives and its oak and mahogany floor with central inlaid patera.
The flanking Castlereagh room, originally the dining room and later the library, has been filled with items relevant to the life and times of Lord Castlereagh - the 'Winston Churchill' of British politics during and after the Napoleonic War.
The Dining room
Morrison's principal reception rooms - the dining room and the drawing-room flank the south and north elevations respectively. They are both spacious, long, rectangular rooms and set against the dining room walls are the twenty-two Empire chairs which were used by the delegates to the Congress of Vienna in 1815. The backs and seats of the chairs were embroidered by nuns in Nantes for Edith, 7th Marchioness, depicting the arms of those present and the nations they represented.
King Edward and Queen Alexandra would have dined here when they visited Mount Stewart in 1903. One wonders whether the 6th Marquess, in the presence of the King, indulged his famed habit of eating dinner as rapidly as possible - a habit which understandably made him very unpopular with guests whose plates were often whisked away by footmen before they had tasted anything.
The Drawing room
The vast drawing-room, with ionic column screens at each end, remains much as it was after being decorated in the 1930's by Edith, 7th Marchioness, who like her mother-in-law before her was one of the great political hostesses of the time. The furnishing comprises quite a mixture of pieces from different periods, including Carrara marble urns and vases, tripod candlesticks, carved standard lamps, sofas, armchairs, occasional tables - all grouped informally as if the house guests were expected to return at any moment.