With all the water that we have received in June there were quite a few of these "fairy" mushroom rings that popped up in our yard. Here is a random folklore picture.
Fairy rings also occupy a prominent place in European folklore as the location of gateways into elfin kingdoms, or places where elves gather and dance. According to the folklore, a fairy ring appears when a fairy, pixie, or elf appears. It will disappear without trace in less than five days, but if an observer waits for the elf to return to the ring, he may be able to capture it.