A fairy ring is a naturally occurring ring of mushrooms. They are also known as pixie’s rings, faerie circles, or elf circles. The English believed that fairy rings were where fairies came to dance and celebrate, the mushrooms of the rings were used as stools for the fairies to recuperate during the evenings festivities. (OP)
The most strongly supported theory about fairy rings is that they are really one large, interconnected mycelia organism. A spore starts in the center and grows outward uniformly, and a ring is formed when the fungus pops above ground in the form of a mushroom. There’s one in France that is 600m (~2,000 ft) in diameter!