Penrhyn Castle, an early nineteenth-century neo-Norman castle (nprn 16687), is located on the Menai Strait, to the north of Llandegai. It lies centrally within a roughly circular park which retains much of its nineteenth-century character, though it is likely that parks were attached to predecessor houses from the medieval period onwards. Existing woodland formed the basis for extended plantations when enlargement and alterations to the layout were made by George Hay Dawkins Pennant, the builder of the present house. The area around the castle remains mostly open lawn as originally designed, with garden areas (86440) at a little distance, and the park surrounding the whole.

The park is bounded by the mouths of the Afon Cegin and the Afon Ogwen, on the west and east respectively, by the village of Llandegai on the south, and by the sea on the north. The ground rises towards the centre of the park, levelling out into an exposed, flat-topped ridge with a couple of knolls. From the top of the house keep and towers almost the whole of the park is visible, though the home farm, to the south-west, is screened by trees.
The entire park is walled, with several entrances and three imposing lodges contemporary with, and in similar style to, the castle: on the south the Grand Lodge on the main, arched, entrance at Llandegai (13448); another nearby at Talybont (on the original rear drive); and another on the north-west at Porth Penrhyn (13310). The retaining sea wall on the northern boundary has an artificial mole (a projecting causeway) which once had bathing huts and hot and cold baths (405439).

The home farm was moved to the south-west from a site to the north, and there is farmed parkland around it. Areas of more ornamental parkland lie to either side of the Afon Ogwen to the north-east, east and south-east. A nineteenth-century print shows deer in the park though no area was designated as deer park.

Woods have been planted along the sea-edge and alongside most of the drives as well as for screening and shelter purposes. The woodland, now commercially managed, is mainly concentrated around the park edges and alongside the main drive. Few parkland trees remain. Deciduous trees, including ash, lime and oak, are generally planted singly, though there are a few groups, and the remaining conifers (of which there are now few) are mostly in groups. The remains of extensive walled gardens, surrounded by woodland, lie within the park (16692; 700209). A visitor area with car parking, buildings and several glasshouses has been built in woodland to the south-east of the house.  

Along the western edge of the park are the remains of an incline and tramway that carried slate from quarries near Bethesda (which paid for the house) to the purpose-built Port Penrhyn at the north-west corner of the park (see 409693 & 306314).

Sources:
Cadw 1998: Register of Parks and Gardens of Special Historic Interest in Wales: Conwy, Gwynedd & the Isle of Anglesey, 250-7 (ref: PGW(Gd)40(GWY)).
Ordnance Survey second edition six-inch map: sheet Caernarfonshire VII.SW (1887).
Additional notes: D.K.Leighton.

Penrhyn Castle, with its park and gardens, is part of the Slate Landscape of Northwest Wales World Heritage Site, Component Part 1. Penrhyn Slate Quarry and Bethesda, and the Ogwen Valley to Port Penrhyn. Inscribed July 2020.
It is now a World Heritage Site https://www.llechi.cymru/

RCAHMW, 26 May 2022