Maybe it's relevant, maybe it's not, but there are a number of distinctive conical hills near Old Radnor: Stanner Rocks, Worsell Wood, Hanter Hill. Apparently these contain some of the oldest rocks in Wales - Precambrian and 700 million years old. Old Radnor was called 'Pen-y-Graig': 'head of the rock'. The geology means Stanner Rocks supports some pretty strange and rare plants, and it was said: "by the common people it is called the Devil's Garden." You can't help wondering where the stones for the local monuments came from. Probably.
"The Cambrian Balnea: Or Guide to the Watering Places of Wales, Marine and Inland" by Thomas Jeffery Llewelyn Prichard (1825).
Extracted from "Betwixt & Between" by Mary Dodsworth and Iain Steele in "The Cauldron" no.115), themselves drawing on "The Folklore of Radnorshire" by Roy Palmer :-
Beguildy church, on raised site by River Teme, probably a B.A. settlement.
Bleddfa church on a B.A. mound.
Bryngwyn: The Six Stones near N boundary of village is a stone circle of ~12 stones.
Llanfihangel Cascob cut into a burial mound.
Llanfihangel Cefnllys a B.A. site. I.A. fort on Cefnllys Hill turned into mediaeval castle.
Discoed church south of a five millenium old yew - a circular site about an antient mound and a Neolithic tree.
Disserth church a circular site with a well nearby formerly dressed with mistletoe.
Kinnerton church within an earlier circular wall. By the road to Old Radnor there is a standing stone.
Llanbister church has tower behind altar, at the E end. Sulfur well overlooks church.
Llandegley church very late, healing well on Cymaron riverbank side nearby.
Llandeio Graban tower bedroom for last Welsh dragon.
Llandewi Ystradenni. Giant's burial at Tomen Beddugre nearby.
Llanelwedd church has thity tumuli within half-a-mile and a lost standing stone.
Llanfihangel Nant Melan ringed by ancient yews, with one holding solitary remnant of a stone circle.
Nantmel church has 6 two millenia old yews in precinct. 2 standing stones called the Devil's Clogs on nearby Tan-y-cefn farm.
Old Radnor church font cut from fifth stone of Four Stones group at edge of Kinnerton-Walton road. In 1994 a vast stone circle revealed from the air in the Radnor valley - probably defined by 1400 oaks, it covers 34 hectares but doesn't have a precise location !
Pilleth church has well behind that was resorted to by people with eye problems.
St. Harmon chuch first dedication in Wales, but he wasn't buried in Bedd Harmon near it. Two stone circles also near, though Cwm y Saeson only has two stones left out of 14 and that on Hendre Rhiw farm only one of 5. Dogs and people treated by sulfur spring on Temple Bar farm.
Whitton church lies in an earlier circular llan.
Visited on 13.2.10. Easy to access in field next to crossroads - approximately 20 metres from gate into field. Can be easily seen over hedge from lane which runs past the stones (on right) with farm a bit further on (on left).
The site is very overgrown now,hardly recogniseable .I didn't realise I had found it at first,the large boulder giving it away,the heather hiding all the other stones. The mound can be made out only because of it's surrounding ditch causing a gap in the undergrowth.
A bit of a trek to get here up very steep slopes,and not easy to find without a GPS. It's about 100 meters from a track and a small pond,but invisible from more than about 50 meters away.
Good views though.
In "The Ancient Stones of Wales" by Chris Barber and John Godfrey Williams (1989 Blorenge Books), this is given the alternative name the Dragon Stone or Serpent Stone. However, the description given doesn't match the other posts:
"This stone stands about 2.5 feet out of the ground and is 4 feet long and 2 feet wide and is near a roadway leading to a farm. It is a slatey-blue stone with seams of white quartz a few inches thick and should be called the Serpent Stone according to a local farmer interviewed by J.G.W. in March, 1963."
"A stone circle, 24-22m in diameter, comprising eleven earthfast stones, c.0.2m high, and a natural boulder. Eccentric within the circle is a ditched mound, 8.0m in diameter and 0.5m high."
These are very low stones, suggesting this could as easily be some kind of ring cairn or kerb.