Plas Tan-y-Bwlch is situated on the north side of the Dwyryd valley, in the western part of the Vale of Ffestiniog (aka Vale of Maentwrog), part way up the steep valley side. It is notable for the survival of a more-or-less intact mid-Victorian landscaped estate of house, garden, wooded park, valley and estate village, set in the magnificent scenery of the Ffestiniog area of north Wales, within the Snowdonia National Park. 

Plas Tan-y-bwlch mansion, an eighteenth-century house enlarged in the nineteenth (nprn 28687), is located towards the south-east boundary of its parkland, and is surrounded by gardens (28688). The landscape here has a history of development from at least the later eighteenth century but the surviving layout of park and garden was largely created between 1869 and the start of the twentieth century after the estate came into the hands of the Oakeley family who owned several local slate quarries: Holland's, The Welsh Slate Company and Gloddfa Canol. The local landscape was written about, and painted, by the noted tourist Thomas Pennant who visited Plas Tan-y-bwlch in 1773. 

The designated parkland forms an irregular oval, long axis east by west. It is bounded on the south by the A487 road above the river, with a section adjoining the river below Tan-y-bwlch hamlet, on the east and north by the minor road to Rhyd, and on the west by the rising ground of Hafod-y-Mynydd. 

The park around the house falls roughly into three parts: the woodland on the steep slope above and behind the house (Coed y Plas), and the deer park above and to the west of this, both areas now amalgamated; and the enclosures to the south and east of the gardens which fan out across the slope below the house. The woodland was probably natural oak woodland which was then managed by the Oakeley family with planted larch and fir, some exotic varieties also planted. Trees were added around the edges of Llyn Mair, an artificial lake above the Plas, and at points on the skyline. Llyn Hafod-y-Llyn, north-west of Llyn Mair, is also an artificial lake. In the woods was created an extensive network of paths many of which remain in use with new ones recently added.  

The Ffestiniog Railway, which passes through the park in a wide loop, was opened in 1835. An area on the flatter land within the loop was made into a deer park. An area of about 218 acres, it was enclosed by walls, now mostly collapsed, with gates for access. It is now mostly planted with conifers with some residual deciduous trees. The mill pond, which lies below, and predates, Llyn Mair, serviced the flour and saw mills below it (401913 & 405431). The small valley of the mill stream was itself a decorative feature planted with ornamental trees, the stream flowing over a series of artificial falls designed to be viewed from the drive which passes down it.

There were at least four drives at different times. The main approach now is from the north-east, with the lodge and gates opposite the Oakeley Arms (715), the most scenically effective drive hacked out of the rock face. The north drive is from an entrance and lodge below Llyn Mair (300232), now disused except as a footpath, passing down the mill stream valley. A later south drive passed the kitchen gardens from an entrance off the A487, with a lodge a short distance along it (300233). A track from the home farm, which formerly curved across the eastern part of the enclosures below the house, was also an early drive.

This area is part of the Slate Landscape of Northwest Wales World Heritage Site, Component Part 5: Ffestiniog: its slate mines and quarries, slate town and railway to Porthmadog. Inscribed in July 2020.  

Sources:
Cadw 1998: Register of Parks and Gardens of Special Historic Interest in Wales: Conwy, Gwynedd & the Isle of Anglesey, 274-81 (ref: PGW(Gd)31(GWY)).
Ordnance Survey 25-inch map, sheet: Merionethshire XI.8 (1888).
Louise Barker & Dr David Gwyn, March 2018. Slate Landscapes of North-West Wales World Heritage Bid Statements of Significance. (Unpublished Report: Project 401b for Gwynedd Archaeological Trust).
Tirwedd Llechi Gogledd Orllewin Cymru / The Slate Landscape of Northwest Wales. Nomination as a World heritage Site (Nomination Document, January 2020). 
Wales Slate World Heritage Site https://www.llechi.cymru/

RCAHMW, 25 April 2022