Merthyr Mawr House (nprn 19319) is situated on a south-south-east facing slope on the north side of the Ogmore river valley, within parkland (700196). The garden and grounds were laid out by Sir John Nicholl between 1806 and 1838, at the same time as the park was created, with some later changes.
The drives, from east and west, arrive at the forecourt, with a grass circle in the north front of the house. The garden and pleasure grounds occupy the core of the park and lie in three main areas: to the south, west and east of the house is the garden; beyond, to the south-west is a belt of wooded pleasure ground extending down to the public road; and to the north are wooded pleasure grounds laid out on Chapel Hill which rises above the house and drives (see 700198).

The garden lies on ground sloping gently to the south and comprises three parts: a lawn and shrubberies to the west of the house, with a summerhouse, an octagonal stone-edged basin, and specimen ornamental trees and shrubs.
South of the house are two revetted terraces with parapets built out over the slope, the upper one paved, the lower one a lawn with a large cedar, and a modern pond with a bog garden formerly planted with bamboos, and beyond it a lawn, formerly with sundial, to the ha-ha on the garden boundary. The east end of the garden consists of several discrete areas: a sloping lawn (formerly a rockery) planted with specimen trees and a shrub border, and with an iron gate into the park;  a small enclosed, rectangular Edwardian rose garden laid out with tile paths, and central ornate octagonal bowl; and further east a sloping lawn planted with fruit trees. The north side of the garden is bounded here by the high south wall of the kitchen garden (700197). Adjacent is a swimming pool, the former boiler house now a changing room.

An icehouse is known to have been situated within the grounds but the exact site is not know; 'filling the ice-house' is mentioned in early nineteenth-century estate records. The structure today known as an ice-house is a purely above-ground shed with a pitched roof.

Sources:
Cadw 2000: Register of Parks and Gardens of Special Historic Interest in Wales, Glamorgan, 14-18 (ref: PGW(Gm)12(BRI)).
Ordnance Survey first-edition six-inch map, sheet: Glamorgan XL (1876).
RCAHMW air photos: 955059/51-2
Sylvia P. Beaman and Susan Roaf, The Ice Houses of Britain, p.531.

RCAHMW, 23 May 2022