What group or religion (or cult) would ociate with something like this? (details)?

I was walking in the woods with my friend and we stumbled upon a clearing and there was a big circle of stones surrounding the area. In the center there was a fire pit with a pentagon circling it mad out of twigs and stuff. sitting on one of the stones i found a man made shield ( it looked like on anyways) My friend have previously been back there several times and he said that there is something different there every time he goes there so there is definately a group of people going back there. The site is about 100 feet from a cemetary but well hidden. What kind of religion, practice, or even cult could be congregating there?