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.