Cefn Mably House, a mostly eighteenth-century house now converted to private appartments (nprn 18286), is located on the north-west side of the Rhymney valley, to the north of Cardiff. It lies within a medium-sized landscape park set on rolling ground (700159). The house itself is surrounded by gardens comprising formal terraces and informal wooded grounds which developed from the eighteenth century onwards but may have origins in the sixteenth century. 

Terraced gardens adjoin the south-east front of the house, on ground falling away to the south and east, the main entrance drive winding through the grounds from the east. Immediately in front of the house is a large, square, revetted grass terrace with a low parapet, extending from the west end to just east of the front door, a small square turret in the south-east corner; to the east, below steps, a smaller square level area and, at the same level, a narrower terrace extending southwards to the south boundary of the garden, with a gazebo in the south-east corner at the end of a central path. The third and lowest terrace lies at the east end of the gardens, to the east of the middle terrace, reached by a wide flight of steps in the north-west corner. The latter, known as the Winter Garden in 1910, is a quadrangular level area of grass bounded on the west and north by high revetment walls. The south side is the boundary wall of the garden with a low parapet. In the middle of the north side is a small pavilion.
The second main area of the gardens is the wooded grounds to the east of the house. A large area, sloping to the east, is laid out informally with specimen coniferous and deciduous trees and an underplanting of evergreen shrubs. Mature trees include cedars, pines and wellingtonia.
The third area is the wooded grounds to the west and south-west of the house. Close to the house later buildings have obliterated much of the historic grounds here. Beyond this area, to the north and west, are wooded grounds through which run the west drive, and in the middle of which is situated the kitchen garden (700160). Much of this area has been redeveloped though many large specimen trees survive with evergreen shrub underplantings, particularly between the house and the kitchen garden. Most former paths have been erased. A dovecote that formerly stood near the east end of the woodland has also gone (37492). To the south of this area, down a small defile (‘Gilbert’s Well’), is a belt of woodland running southwards, some mixed deciduous trees and some large conifers, with evergreen underplanting.

Sources:
Cadw 2000: Register of Parks and Gardens of Special Historic Interest in Wales, Glamorgan, 24-8 (ref: PGW(Gm)11(CAE)).
Ordnance Survey Second Edition 25-inch map, sheet: Glamorgan XXXVII.12 (1875).

RCAHMW, 13 May 2022