Near Cnoc Gréine's summit, on the side away from the retreat huts, there is a spring source under a volcanic extrusion of basalt. Adjacent to its pool are a series of downward "stepping" wet terraces, once used for herb & healing plant cultivation by the women called "Grian's Daughters."
The pool is still refreshed by the spring coming from below the basalt escarpment below my feet, and its surface can be seen immediately adjacent to the two large artificially-place stones that act like a pier. The pool is now mostly choked with water plants, but had areas of open water.
In the distance can be seen the artificially-levelled meadow at the base of the hill, able to accommodate several thousand people, which I call "Grian's Apron." It is about 200 metres below.