I came across a group of fairy rings in the spruce plantation in Gosforth Park Nature Reserve. There are several up to 10m in diameter but none is quite complete. This was the best I could find.
Others made less than a complete circle.
I'm not sure what kind of mushrooms they are. They look tasty enough but I didn't try them. One possibility is Clitocybe nebularis (clouded agaric) which often makes fairy rings.
Fairy rings have been thought to be magical places. In France they are ronds de sorciers (sorcerer's rings) and in Germany Hexenringe (witches' rings), both of which sound rather more sinister. You can read more about fairy rings here.