Llyn Gwyn Enclosure

Has been described as a Questionable Timber Castle (Motte Ringwork)

There are earthwork remains

NameLlyn Gwyn Enclosure
Alternative NamesTreflyn
Historic CountryRadnorshire
Modern AuthorityPowys
1974 AuthorityPowys

A semicirclar run of bank and ditch defines an enclosure, c.50m by 24m, otherwise resting on a relict lake-bank scarp to the SW. (Coflein as ?Iron Age defended enclosure)

Crescentic bank and outer V-shaped ditch. Open end abutting old NE bank of lake. About 80m by 30m. Probably defensive site (Ditch possible originally water filled). Traditional association with Strata Florida Abbey. (Clwyd Powys Archaeological Trust HER as medieval defended enclosure)

The Llyn Gwyn Earthwork consists of a crescent-shaped bank with an outer V-shaped ditch, enclosing an area of c.50m by c.24m. The scarp along the otherwise open south-west side probably represents the original bank of the lake, which is somewhat smaller today, and the ditch may have been water-filled. The remains are not especially diagnostic as to date, though they are traditionally associated with Strata Florida Abbey. (Scheduling Report - Site Type - Earthwork (unclassified): Period - Unknown)

Gatehouse Comments

The Castles of Wales web site has a database which states, under the name Treflyn (aka Llyn Gwyn) at SO012650, 'small motte visible' but gives no authority. Nothing in the official descriptions or on the air photo suggests a motte here. The original form of the earthwork appears to have been a oval ring-bank half of which has been eroded away, presumably at a time when the lake was somewhat larger. The actual nature and function of the site is obscure but a medieval residence of a water bailiff may be a vague possibility.

- Philip Davis

This site is a scheduled monument protected by law

Not Listed

The National Monument Record (Coflein) number(s)
County Historic Environment Record
OS Map Grid ReferenceSO012650
HyperLink HyperLink HyperLink

No photos available. If you can provide pictures please contact Castlefacts

Most of the sites or buildings recorded in this web site are NOT open to the public and permission to visit a site must always be sought from the landowner or tenant.

Calculate Print


  • RCAHMW, 1913, An inventory of the Ancient Monuments of Radnorshire (HMSO) p. 118 no. 480 online copy


  • Savory, H.N., 1954, Bulletin of the Board of Celtic Studies Vol. 15 p. 74, 307