Machen House, a building of 1831 in late Georgian style (nprn 310430), is located to the east of Caerphilly on the north side of the A468. Its gardens lie to the north, east and west of the house, adjoining the churchyard of St Michael's Church (307316) to the east. The drive enters the grounds on the south side through sandstone gate piers, entrance gate and stone garden walls. The curving drive approaches the house to a turning circle on its east side.

The garden covers about two acres, enclosed by a stone castellated wall with several mock turrets. The layout of the garden is largely informal with winding gravel paths, two artificial, naturalistic ponds, specimen trees and shrubs, and lawns. The easternmost pond appears to be designed in the style of a 'willow pattern' garden with a 'Chinese' bridge spanning the southern end. In the middle of the pond is an original iron fountain. The pond to the north-west has a central rockwork fountain and a rockwork cascade, also original features. A small summerhouse, to the west of the house, with iron columns on its open side, is also part of the original layout.

The garden to the north of the house is now lawn. Near the north-east boundary is a free-standing Gothic garden structure, of stone with three arched niches each with two slate shelves for bee skeps; it is probably contemporary with the house of 1831, but may be earlier. A wood to the north of the garden was also laid out as a wild garden with a pond, walks and some evergreen planting; this is now largely overgrown.

The former walled kitchen garden is situated to the west of the garden. Its east boundary is the west wall of the main garden, between which there is an interconnecting doorway. It is now a separate private garden.

Sources:
Cadw 1994: Register of Parks and Gardens of Special Historic Interest in Wales, Gwent, p.91 (ref: PGW(Gt)32(MON)). 
Ordnance Survey second-edition 25-inch map, sheet: Glamorgan XXXVIII.1. 

RCAHMW, 20 July 2022