Tyn Twr

Has been described as a Possible Timber Castle (Motte), and also as a Possible Pele Tower

There are cropmark/slight earthwork remains

NameTyn Twr
Alternative NamesTy'n Twr; Twr Abercaseg; Llanllechid
Historic CountryCaernarfonshire
Modern AuthorityGwynedd
1974 AuthorityGwynedd

Ty'n-Twy Tower was a small medieval tower, possibly the Twr Abercaseg mentioned in 1254 that guarded the Ogwen crossing and approach to Nant Frangcon. The tower is mentioned as being transferred to the ownership of the Griffiths of Penrhyn in 1458. (Coflein–Reference: Cadw listed buildings database.)

The tower whose name survives in Pont y Twr and Ty'n-twr was perhaps a motte formed by revetting the boss of rock E of the bridge. Possible traces of an early wall can be detected on the NE, but the ground is now too much built over for certainty (RCAHMW). There is insufficient evidence to identify the 'boss' of rock, which is now densely overgrown as a motte (OS Record). (Gwynedd Archaeological Trust HER)

There is considerable medieval activity on the site, including a probable 14th century building, possibly overlying an earlier structure. Documentary evidence suggests a tower or some building of considerable significance stood on the boss of rock at this site during the 13th century. (Scheduling Report)

Gatehouse Comments

The location, where the A5 main Holyhead-London road comes out of the Snowdonian mountains, is excellent as a toll collection point. The form of the tower is unclear. Was this a timber tower on a rocky knoll or a masonry building (or both at various periods). Does not seem to have been anything more than one building.

- 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 ReferenceSH626660
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  • Salter, Mike, 1997, The Castles of North Wales (Malvern) p. 49 (slight)
  • King, D.J.C., 1983, Castellarium Anglicanum (London: Kraus) Vol. 1 p. 35
  • RCAHMW, 1956, A Survey and Inventory of the Ancient Monuments of Caernarvonshire Vol. 1: East (HMSO) p. 134 (Not numbered but mentioned under the heading) online copy


  • 1993, Archaeological assessment of Ty'n y Twr, Bethesda (Report no. 53, Gwynedd Archaeological Trust)
  • Tony Parkinson, 1993, Notes on Tyn-Twr Tower, Bethesda