it is a beautiful place, i did not get much chance to explore but i am planning on going again this year so will do it properly this time.
i was lead to beleave it was built as art work but built for use seems to make more sense, espeially with the growing popularity of pagan beliefs around the time as you said.
I went up their with a few friends whose idea of a holiday is more pub based... i did manage to get them on a short walk but next time i go im going with some like minded people and im planning on taking in the whole area.
a nice place to sit relax, medatate and just enjoy nature.