Hilston Park is a country house and estate between the villages of Newcastle and Skenfrith in Monmouthshire, Wales, close to the border with Herefordshire, England.

The park includes an early 20th century lodge at each of the two entrance gates; a ruined coach house; a lake, boathouse, and pond; several streams, gardens, and wooded areas; and Hilston Tower, a late 18th-century folly of red sandstone in the grounds's northeastern corner.

In 2020, the councils decided to consolidate their outdoor education facilities on a single site, and Hilston Park was deemed surplus to requirements.

Following this stable period of ownership, accounting for about a century, the estate then changed hands a considerable number of times within the next 70 years.

His son,[4] Captain Pryce Hamilton, brother to Alice Mary Sinclair,[5] seems to have added considerably to the Hilston Estate and it appears that he also purchased Norton Court, Skenfrith from Henry Somerset, 8th Duke of Beaufort, and bought Skenfrith Mill and Lower Dyffryn House, Grosmont around 1870.

In 2020, cost pressures led the councils to decide to consolidate their outward bound activities at a single site near Cwmbran, and Hilston Park was deemed surplus to requirements.

One of these, Lower Dyffryn, is an E-shaped building of Early Tudor style, with a slate roof, three gables, and a projecting chimney-breast.

[11] Cadw cites the reason for it being listed as an SSSI in 1990 as "19th-century park and garden, with some well preserved features, including ornamental lake and folly tower".

The area to the north of the kitchen garden contains mainly ruined sheds and glasshouses and was wildly overgrown at the time of its surveying in December 1990.

[10] The lake, roughly 100 metres (330 ft) at longest from north to south and roughly 60 metres (200 ft) at its widest point, is cited by Cadw to be "fed by a spring at its [north] end, and dammed at its [south] end by a massive earthen dam across the valley floor.

[10] There is also a woodland, a former Forestry Commission plantation, planted around 1960 in the north-eastern corner of the park on a small hill, which contains a circular folly tower, of three storeys, in the centre.

[13] The two-storeyed north front features nine bays, the outermost ones slightly recessed, with a central pedimented porte-cochère of four massive Ionic columns.

[13] The building was extended on its eastern side and its interior remodelled, around 1912, when a large ballroom in the Arts and Crafts style, designed by Arthur Grove was added.