The improbably situated hut circle, at the bottom of the sink hole. Image credit: A. Brookes (3.8.2013) thesweetcheat Oct 2, 2013
That's brilliant, bonkers and definitely on the list.
Lots of good stuff around and about, worth a trip. Llorfa is close too (went there last weekend), Cribarth, Saith Maen, Maen Mawr, etc.