Plas: "Palace" or "Mansion"
Rhianfa: "Rhiannon's Place" or "Rhiannon's Domain"
Therefore, the full meaning of "Plas Rhianfa" is "Rhiannon's Palace" or "Rhiannon's Mansion."
Rhiannon is a Welsh goddess associated with horses, magic, and the moon. It's a beautiful and evocative name, and the combination with "Plas" suggests a grand and historic place.