I Dunno if it’s the same place, but the only ref I’ve ever seen to a circle on Man is Meayll Hill:

Some stuff on it here if you scroll downaways:
http://www.isle-of-man.com/manxnotebook/fulltext/ma1904/pt2.htm

There’s a blurry bit of an old map on the page, and I couldn’t make out any bridge, so it might be somewhere else.