Hillsborough Castle, The Square, Hillsborough, County Down, BT26 6AG

Hillsborough Castle is a detached Neo-classical large house of two and three storeys, built on an L-plan and arranged around a front courtyard on the west side of The Square. The west wing was constructed around 1780, the east wing added around 1795, and a Giant Ionic portico was added to the south garden front around 1835. The building was originally constructed as the seat of the Marquesses of Downshire. The demesne was sold to the state during the 1920s and renamed Government House. The house was damaged by fire in 1934, and the interior has undergone a succession of reinstatement works since that time.

The building is constructed of red sandstone ashlar with a projecting plinth course and moulded sandstone cornice to a lead-lined parapet wall. The roofs are hipped natural slate with lead ridges, and there are several tall sandstone ashlar chimneytstacks with clay pots set behind the parapet wall. Lead hoppers break through the parapet wall with lead downpipes to the main elevations and cast-iron to the remainder. Window openings are square-headed with sandstone sills and contain timber sash windows, though some have been replaced with security windows. Lead-lined roofs incorporate cast-iron rainwater goods to secondary elevations.

The west wing comprises a central two-storey block seven windows wide with a pedimented breakfront three windows wide, flanked by a pair of single-bay projections—two-storey to the south and three-storey to the north. The north projection extends into a further three-storey wing over basement, two windows wide. Sandstone architrave surrounds with pediments on scrolled console brackets frame the central opening and ground floor windows to the south projection and the re-entrant bay of the north projection. The ground floor contains 6/9 timber sash windows except for the central opening, which has timber French doors with a six-pane overlight opening onto four nosed steps. The first floor has security windows, with 3/3 or 3/6 timber sash windows to the remainder. The central block opens onto a gravel terrace with nosed stone steps at either end leading to formal gardens. The north wing has two painted gabled elevations to the north, each with a tall sandstone chimneystack, and a lower flat-roofed central connecting section. A single-storey over basement laundry wing with hipped natural slate roof and 6/6 timber sash windows abuts the front pile of the north wing. The east elevation is four windows wide and three storeys tall with rendered walling and timber sash windows, abutted by sandstone accretions extending from the east elevation of the east wing.

The east wing presents a symmetrical two-storey elevation five windows wide with a slight breakfront fronted by a tetrastyle Ionic portico and flanked by a pair of single-bay three-storey decorative projections. Security windows occupy the first floor, with a pair of large round-headed window openings to either end bay containing tripartite timber sash windows and fanlights over. The portico comprises paired Ionic columns supporting a full entablature with a central square-headed door opening with pediments on scrolled console brackets and double-leaf flat-panelled timber doors. The door is flanked by a pair of 6/9 timber sash windows. Wall-mounted coat-of-arms stone plaques and a cast-iron wall-mounted post box are positioned on the portico. The projections at either end have a breakfront bay to the upper floors on both elevations, supported on decorative console brackets, with French doors to the ground level and 3/3 timber sash windows.

Facing the front courtyard, the two-storey east wing presents an informal composition to its north elevation, seven windows wide, with a two-storey projection at its east end abutted by a further two-storey over basement with attic block extending further east and fronting onto The Square. Extending from the south projection of the west wing is a flat-roofed single-storey gallery five windows wide, terminated by a tetrastyle Ionic portico to an entrance breakfront. This gallery contains 3/3 timber sash windows to the first floor and 6/6 to the ground floor. The shallow portico has four Ionic columns supporting a plain entablature containing a square-headed door opening with architrave surround and double-leaf flat-panelled timber doors flanked by a pair of 2/1 timber sash windows. The east projection is three windows wide and three windows deep, abutted by a flat-roofed sandstone accretion to the east. The three-storey east block steps behind the east projection, aligned with the front gate screen, and is abutted by a flat-roofed entrance porch with a replacement hardwood panelled door. Facing east, the easternmost block is three windows wide with a front garden enclosed by cast-iron railing and a matching pedestrian gate.

The south garden front presents a symmetrical two-storey elevation fifteen windows wide with a pedimented tetrastyle Giant Ionic order portico and a pair of shallow two-storey three-sided canted bays. A balustraded parapet wall fronts the central section with a plain parapet wall to the remainder. The first floor contains 3/3 timber sash windows (replacement security windows to the west end) with 6/6 to the ground floor. The prostyle portico has a lead-lined roof and sits on a crepidoma-style platform of five nosed steps. The soffit of the portico features stepped coffering with a tripartite central opening with cornice supported on scrolled console brackets, containing security-glazed French doors and sidelights opening onto three nosed steps. A further slender window opening sits to either side with a small central window opening to the upper storey. The portico opens onto an elevated gravel terrace spanning the full south garden front, with a series of nosed stone steps descending to stepped garden terraces. To the east end of the terrace stands a Greek temple-style Summer House facing west.

The setting comprises the building laid out around a front courtyard on the west side of The Square, enclosed by an elaborate gate screen. The formal west and south fronts are positioned on an elevated site with formal landscaped gardens on a gradient, enclosed to Dromore Road by a tall sandstone ashlar wall and enclosed to the rears of houses on Main Street by the former Stable Yard. Sandstone low walling and balustrading front the elevated south terrace with stone steps leading to the formal gardens.