Cader Berwyn Cairn I is a round cairn, 28m in diameter and 2.4m high, surmounted by an OS triangulation pillar, set upon the summit of Cader Berwyn, and serving to mark the county boundary.

(source Os495card; SJ03SE6)
RCAHMW AP955008/67
J.Wiles 26.09.02

Description confirmed during Uplands Survey visit Dec 2006. Stone pile marked on 1st ed OS map. (A.C.K. Roseveare & N.A.R. Vaughan, AP, 29/03/2007)