A seat of 5th Earl Of Orrery (a friend of Dean Swift), who described the house hero (1738) as "old, low, and though full of rooms, not very large". Sold by 7th Earl to James Alexander, a wealthy East Indian "Nabob", who subsequently became 1st Earl of Caledon; and who replaced Lord Orrery's house with a house built on different site, to the design of Thomas Cooley 1779. 2 storey; 7 bay entrance front with pedimented breakfront centre; garden front with 1 bay on either side of a broad central curved bow, the downstairs window in each of these bays being of the so called Wyatt type, set under a relieving arch; 5 bay side. The plan has a strong resemblance to that of Mount Kennedy (qv); a large hall with a screen of yellow scagliola Doric columns at its inner end, a Doric frieze and plasterwork in the Wyatt manner on the walls and ceiling, opens into an oval drawing room extending into the garden front bow. On one side of the drawing room is the dining room; on the other, a boudoir with a slightly vaulted ceiling of delicate plasterwork in "Harlequin" style, coloured in chocolate, scarlet, apple green and tortoiseshell, incorporating a circular painted medallion; the walls of the room being hung with an apple green Chinese or "India" paper which was probably brought back from the East by "Nabeb" Alexander himself.

In 1812, 2nd Earl enlarged and embellished the house to the design of John Nash. 2 single storey domed wings or pavilions were added, flanking the entrance front and projecting forwards from it; joined by a colonnade of coupled Ionic columns, to form a long veranda or stoep such as Lord Caledon had probably grown used to sitting under when he was Governor of the Cape of Good Hope. One of the two wings contains a large and splendid library, with a coffered dome and Corinthian columns of porphyry scagliola. Nash also re decorated the oval drawing room, making it one of the most perfect Regency interiors in Ireland; with friezes of gilt Classical figures and mouldings in cut paper work, elaborately shaped drapery pelmets and mirrors supported by swan necked consoles.

In 1835, towards the end of his life, 2nd Earl carried out further additions to the house, when his architect may have been Joseph Pennethorne, who continued Nash's practice after his death 1834. A 3rd storey was added to the central block, the pediment being replaced at the higher level; and the entrance was moved round to one end of the house, where a single storey extension containing a domed octagonal hall, fronted by a hexastyle Ionic porte cochere, was built; the original hall becoming the saloon. In the park is C18 Bone House, its pillars and arches faced with ox bones; the only surviving relic of 5th Earl of Ossory's rococo garden. Towards the end of C19, the park was inhabited by wapiti and black bears, brought back by 4th Earl of Caledon who had hunted and ranched in the Wild West. His 3rd son was Field Marshal Earl Alexander of Tunis, whose boyhood was spent here.