Ffynnonwen was discovered during aerial reconnaissance in 1996 by Chris Musson, RCAHMW, and showed a large oval enclosure with an entrance to the west within which, in the south-west quadrant, lay a circular enclosure with and apparent north-facing entrance. Geophysical survey by DAT confirmed the enclosure as measuring 160m x 140m with a circular inner enclosure measuring 45m diameter. The enclosure was partly excavated in 2006, revealing a four-post structure, the enclosure ditch and other structural remains typical of a late prehistoric settlement. Scarce finds were recovered which included several pieces of slag, part of a glass bead, a spindlewhorl made from re-used Roman Severn Valley Ware and a Mesolithic flint microlith. See interim report by K. Murphy in Archaeology in Wales 46 (2006), 114-118.

A further defended enclosure was also discovered to the east at Treprior (NPRN 410166).

T. Driver, RCAHMW, 26th Jan 2010.