Faery Rings

Faery rings are toadstools growing in a circle. Step inside a faery ring, it is said, and you will travel to Faerie -- perhaps never to return. The rings are made by faeries or elves dancing in circles. 

Stepping inside the ring compels a human to join the wild dance, which may seem to last minutes or a couple of hours or a whole night -- but in fact would last seven years or longer, and the victim may be forced to dance to the point of exhaustion, death, or madness. Some say anyone who steps into a faery ring will die at a young age. 

Faery rings are also known as elf rings, faery circles, elf circles, or pixy rings. In the Welsh and Manx tradition, the faery rings grow overtop underground faery villages. One must not violate a faery ring by collecting dew from the grass or flowers growing there, else he risk misfortune. Destroying a faery ring is fruitless (it will only grow back) and also causes bad luck. 

Humans who are held captive in a faery ring may be rescued by someone who follows the faery music but keeps one foot outside the ring and pulls the dancer out whilst others hold onto his (the rescuer's) coat-tails. 

Other methods for rescuing someone trapped in a faery ring include tossing wild marjoram and thyme into the ring, thus confusing the faeries; touching the victim with iron; or a stick from a rowan tree may do the trick. 

Bibliography: Faeries by Brian Froud and Alan Lee
Webography: Wikipedia (https://en.wikipedia.org/wiki/Fairy_ring).
The above image was found on Google (https://www.google.com/#gs_rn=17&gs_ri=psy-ab&gs_mss=faery%20ri&tok=8idwsvsGPsHmvQCaqJX9gA&suggest=p&cp=11&gs_id=1e&xhr=t&q=fairy+rings&es_nrs=true&pf=p&sclient=psy-ab&oq=faery+rings&gs_l=&pbx=1&bav=on.2,or.r_cp.r_qf.&bvm=bv.48293060,d.eWU&fp=d0df36031120a59a&biw=1024&bih=600).