Belfast Castle, Antrim Road, Belfast, BT15 5GR

Belfast Castle is a detached, multi-storey Scottish Baronial style castle built in 1870 to the designs of architect John Lanyon for the Marquis of Donegall. The building comprises a three-storey main block with attic over basement, a four-storey corner tower to the southwest with basement, and a single-storey wing to the northwest, also over basement. It is constructed from random rubble coursed sandstone with fine lime pointed joints and ashlar sandstone dressings throughout. The building sits on an elevated site on the southern slope of Cave Hill, overlooking Belfast City to the south.

The castle features multiple pitched natural slate roofs with roll-moulded black clay ridge tiles and lead valleys set behind crow-stepped gables with ball finials and Irish crenellated parapets. Shouldered profiled sandstone ashlar chimneystacks with clay pots rise throughout. Tourelles to most corners have conical slate roofs surmounted by lead caps and iron finials. Moulded cast-iron guttering runs along a moulded sandstone eaves course, with cast-iron downpipes. A projecting plinth course with chamfered sandstone trim runs around the base, with a continuous string course over the ground floor. Window openings are generally square-headed with stop-chamfered smooth sandstone ashlar surrounds, flush splayed sills, and single-pane sliding timber sash windows featuring slender ogee horns.

The west entrance elevation is dominated by a three-bay tower to the right with two-storey recessed sections to the remaining elevation and a central entrance portico. A colonaded portico with flat roof and arcaded parapet wall is supported on paired Doric columns with fluting and strapwork, set on plinth walls with matching Doric pilasters flanking the entrance. Double-leaf hardwood doors with deeply set panels are set within a shouldered door surround with a decoratively carved tympanum depicting a shield yielding animals and a banner stating 'INVITU SEQUITUR HONOR', framed by engaged pilasters and arch moulding with a crowned ancon over. The arcaded parapet continues along the north face of the entrance bay, returning to enclose a glazed roof to the Deerpark Room. A full-height clasping round tower stands at the southwest corner, with a tourelle and corbelled-out crow-stepped gable on corbels at the northwest corner of the four-storey tower.

The gabled north elevation of the tower rises to a chimney stack with a semi-circular tower to the left surmounted by corbelled-out crow-stepped gabled section. To the northwest corner is a clasping corner oriel set at 45 degrees, with an ashlar sandstone hipped roof. The Deerpark wing has a square-headed door opening with timber panelled doors and coloured glazed fanlight, with matching window to the left opening onto concrete steps and landing bridging the basement area. At basement level is a square-headed door opening with timber panelled door and shouldered sidelights set in a smooth sandstone surround with relieving arch over. The single-storey northwest wing is set behind a decorative screen wall and has a steeply pitched roof with louvered dormer and iron finial, featuring 4/4 pane sliding timber sash windows.

The four-storey gabled north elevation features a dominant full-height clasping tower to the left. The two-storey wing to the right has a full-span crow-stepped gable to both elevations with a squat tower to the right, corbelled-out balconette to the left, and 2/2 pane sliding timber sash windows. The five-bay three-storey east garden elevation with attic features a clasping tower to the right and tourelle to the left, both with conical roofs, and a central semi-circular bay window. Three crow-stepped gables rise above eaves level with a matching wall-head dormer. The central bay window is corbelled out to the base with a single supporting pier and has lead-roofed dormers to either side of its conical roof, with 3/3 pane bowed sliding timber sash windows. The upper ground floor has a pair of door openings to either side of the bay window with double-leaf timber glazed French doors opening onto balustraded corbelled balconies. Two flights of curving stone steps with elaborately carved string, supported on a diminutive stone arch, join as a spiral stair in front of the bay window with a central column and terminate at two circular stone newels. These stone steps were added around 1894 and were also designed by John Lanyon.

The three-bay three-storey south garden elevation with attic is dominated by an advanced five-storey crow-stepped gabled corner tower. A central crow-stepped gable rises above eaves level with matching wall-head dormers to either side. A corbelled-out oriel window to the right has a sandstone openwork parapet. The tower features a full-height clasping corner tower and an angled oriel to the right with a corbelled balcony spanning the tower.

The castle is set on an elevated site on the southern slope of Cave Hill with formally laid out gardens to the south and east. A circular fountain to the south garden features geometrically laid-out paths and mosaic panels. The gardens are enclosed to the west by a tall crenellated sandstone retaining wall with bifurcating stone steps terminating to the south at a turret with conical slate roof and iron finial, having a shouldered door opening with sheeted timber door. The west entrance elevation is approached from the south by a bitmac avenue passing the south garden and opening onto the Cave Hill Park avenue via iron gates hung on octagonal corniced sandstone pillars with steel lanterns, with a matching pedestrian gate to the west hung on iron posts. The avenue opens onto Cave Hill Park via a further pair of gates at the north perimeter, also hung on octagonal stone pillars. The entire site is enclosed by iron railings and security palisade fencing. The two sets of octagonal pillars at the gates were likely installed around the 1970s during improvement works to the castle, though the gate screen at the site entrance at the top of Innisfayle Park, which also has octagonal stone pillars each surmounted by ornate carvings of a hound bearing a plaque, is more likely to be original, though possibly relocated.