What you cannot see on the side of Ysgyryd Fawr in the above scene is any sign of a cleft left after a landslip. Alternatives to the scientific explanation abound too and one of the more fanciful ones is that it was a resting place for the biblical Noah's Ark. Christian symbolism is common around here with names like Nazareth and Bethlehem being attached to places.
The photo dates from a weekend visit to the area in June 2014 when I stayed in Abergavenny while exploring around both Ysgyryd Fawr and the Sugar Loaf. The latter was known to me as you will see from other entries in the album and there are other ports of call like Blorenge for a future visit too. It has been a while since the last one so a return is overdue.