Plas yn Rhiw stands at the foot of Mynydd Rhiw, looking out across Porth Neigwl and Cardigan Bay to the Llyn Peninsula curving away to the south. The location has been inhabited for far longer than any of its visible buildings. Neolithic remains in the surrounding area date back roughly 4,000 years; Celtic forts within 2 km of the manor house testify to local settlements some 2,000 years ago. Roman legionaries from Segontium near Caernarfon - an outpost of the Legio XX Valeria Victrix - had defensive structures whose evidence survives nearby, and 6th-century Christian foundations like St Hywyn's at Aberdaron are part of the same long pattern of habitation. It is believed that the present manor house stands on or near the site of an earlier defended house, built by Meirion Goch in the 10th century to prevent Viking incursions into Porth Neigwl. Whether that lineage is exact or partly mythic, the location has been occupied continuously for as long as people have lived in this part of Wales.

The house itself is small. Its core is early 17th century, Tudor in spirit with later Georgian sash windows added. It stands in roughly one acre of garden, with a detached cottage, a summerhouse and a tool shed nearby. There is an old mill beside a small stream that once held royal permission to grind its own corn. The whole thing is a working manor at the smallest credible scale - the architecture of a minor Welsh gentry family rather than the great houses of the English shires. What it gives up in size, it makes up in setting. From the front lawn, you look out across Porth Neigwl to the Atlantic; behind, the hill rises sharply. The garden is terraced into the slope and divided by clipped hedges into small compartments - a series of outdoor rooms, each with its own planting scheme, descending toward the view.

The Keating sisters were not professional gardeners, but they took their garden seriously. Clough Williams-Ellis, who lived not far away at Plas Brondanw and was busy creating his Italianate village at Portmeirion further up the coast, advised them. The result is a garden of native and cultivated plants in restrained Welsh-cottage style - box hedges, shrub roses, fuchsia, hydrangea, herbs and small flowering trees - that feels as old as the house even though most of it was planted within the last hundred years. The garden is now the only organic National Trust garden in Wales: no chemical pesticides, no synthetic fertilisers, managed entirely by traditional methods. The original garden of roughly one acre has been expanded by the trust to include about 150 acres of surrounding woodland, much of it native broadleaf restoration. The whole estate is managed as a single ecological unit.

The sisters gave Plas yn Rhiw to the National Trust in the 1940s, in memory of their parents Constance and William Keating - while reserving the right to continue living in the house for the rest of their lives. They each did, until their deaths. They are buried in a churchyard near Porth Ysgo, about five kilometres away. The house is now open to the public on a limited schedule through the year. It is the kind of place you can walk through in twenty minutes if you do not stop, or two hours if you do. Most people stop. The small rooms keep the Keating sisters' furniture and books. The garden keeps something of their plantings. From the lawn, the view across Hell's Mouth is the same one they bought it for, more than eighty years ago - a great curve of sand and surf with the Llyn Peninsula running south and the open sea beyond.