Although well seen from the wondrous hillfort occupying the north-western section of Craig yr Aderyn, since this rather obvious cairn, crowning the crags to the approx south-east, was not marked on my 1:25K OS map I assumed it to be modern, possibly the result of quarrying work. Needless to say I'm glad to report that I was wrong. Not only do the people at Coflein disagree re modernity - suggesting a Bronze Age origin - they also cite a possible further ancient enclosure upon said summit. I quote:
'Large stone cairn constructed of scree, with central robber pit, which lies some 300m south-east of the prominent hillfort of Craig-yr-Aderyn. The cairn sits on a rocky crag at the south-western end of possible stone defended enclosure, with substantial scree-built rampart to north-east. Not investigated on the ground. Discovered during RCAHMW aerial reconnaissance on 17th October 2005, image ref: AP_2005_2283. T. Driver, 5th June 2008'
Good reason to return at some point, I guess.... What a drag. As if the sublime views weren't reason enough?