Observatory House, Calton Hill, Edinburgh

Observatory House, Calton Hill, Edinburgh

A Grade A listed building designed by James Craig in 1776 and built to altered plans until the late 18th century, with a major subsequent alteration in 1883.

The building forms an L-plan, rising to three storeys (two storeys on the north elevation). It is constructed in a Gothic and Scots Baronial style, distinguished by a buttressed round tower at the south-west corner, later machicolated and crenellated wings to the east, and a crowstepped wing to the north. The building comprises a 3-bay tower, 3-bay east elevation, 3-bay south elevation, 2-bay west elevation, and a single-bay north elevation.

The 18th-century sections are built in random rubble, whilst the 19th-century sections use squared, tooled, and snecked rubble with predominantly polished margins and droved tabs to openings. The tower buttresses are finished in squared rubble quoins, and the 19th-century sections feature droved ashlar quoins and crowsteps, employing long and short quoins throughout. Fenestration is predominantly regular, with pointed-arched openings and hoodmoulds to first-floor windows, excluding the north elevation.

The south-west round tower elevation presents three bays with two battered buttresses flanking the central bay and a single battered buttress to the outer right. Windows appear only to the left and right bays at ground floor. A corbelled eaves cornice is broken by second-floor openings, with the opening to the left bay featuring lower jamb sections with chamfered detailing and chamfer-stops.

The south elevation spans three bays with a battered buttress to the outer right. Random rubble predominates to the left of the centre bay, with natural rock outcrop incorporated into the wall face; squared tooled snecked rubble finishes the remainder. At ground floor, there is no opening to the centre bay, with a loophole to the right bay. The left and centre bays feature an eaves band, partially covered by lead, and a modern metal balustrade. The right bay is finished with a machicolated and irregularly crenellated parapet, a blind loophole to the right, cable moulding at the base broken to centre by an ornamental cannon, and feather-edged coping.

The east elevation displays three bays with a two-storey setback battered buttress to the outer left. The advanced left bay features a curved return corbelled out to form an arris above first-floor level. At ground floor, a cruciform loophole is present; the parapet is machicolated and irregularly crenellated with a blind loophole to the right, and the base carries cable moulding broken to centre by an ornamental cannon, finished with feather-edged coping. The centre bay contains a re-entrant angle where a forestair from the right leads to the first-floor landing. At ground floor, a timber boarded door with ornamental cast-iron hinges sits in a segmental-headed opening; at first floor, a timber boarded door with ornamental cast-iron hinges and blocked fanlight occupies a segmental-headed opening. A lean-to roofed porch with shouldered arches and chamfered lintels to the east and north, and a chamfered pier to the north-east corner, is present. A small window appears at second floor. A corbelled crenellated parapet is topped with rope moulding at the base and feather-edged coping. The right bay is capped with a crowstepped gable-end topped by a thistle finial, with a curved return corbelled out to form an arris at second-floor cill level. At ground floor, predominantly random rubble contains no openings, with a relieving arch above the second-floor window and a recessed square panel above.

The north elevation has its ground floor obscured by enclosing walls, not visible as of 2002. A curved return corbelled out to form an arris above first-floor level appears to the left. To the right, a canted bay at first floor contains a single triangular-headed opening to each side, with an eaves band, cornice, and pyramidal roof surmounted by a wrought-iron finial.

The west elevation, to its left, features a crowstepped gable-end with a cross finial, random rubble to ground floor, and squared tooled snecked rubble to upper floors, with two windows to ground floor and a relieving arch above the second-floor window. To the right, a projecting section at ground floor contains a loophole, whilst upper floors carry a corbelled-out stair oriel with corbelled and corniced parapet, a blind trefoil to the right, and two windows at half-storey.

Glazing throughout employs 12-pane glazing to ground floor of the tower and south and west elevations. At first floor, predominantly intersecting Y-pattern astragals appear to top sashes, with 6-pane glazing to bottom sashes of the tower, 4-pane glazing to the south elevation, and plate glass to the east and west elevations; plate glass glazes the north elevation. At second floor, predominantly 2-pane glazing appears to bottom sashes and 4-pane glazing to top sashes, with 8-pane glazing to the left bay of the south elevation and the stair oriel to the west elevation, 4-pane glazing to the centre bay of the east elevation, and 12-pane glazing to the tower. All glazing sits in timber sash and case windows. A shallow conical roof tops the tower; pitched roofs cover the north end of the north wing and flat roofs the east wing and south section of the north wing, all finished in graded grey slate with stone skew putts. To the east elevation, a corniced wallhead stack forms part of the parapet to the right of the advanced left section; to the west elevation, a corbelled-out corniced gable-end stack appears to the left, with a corniced stack to the roof between the tower and north wing. Predominantly circular cans are employed.

The interior contains an inner timber and glazed door and screen forming a small vestibule. A closed-well timber stair with quarter landings features acorn finials to newel posts on the upper flight. The first-floor tower room is finished with an ornate cornice, architraved door and windows, and a classical painted stone chimneypiece with decorative tiled cheeks. The second-floor tower room features a plain cornice, an architraved and corniced doorpiece, and a shallow domed ceiling painted with a scene from Norse mythology. The first-floor room in the north wing is decorated with a plain cornice, architraved door and windows, and a classical painted stone chimneypiece with decorative tiled cheeks.