Fiona and the Fairy Ring

When Fiona discovers a circle of golden grass in the forest, her grandmother tells her it is a fairy ring and warns her never to step inside the ring. But that night Fiona hears music coming from the forest and discovers fairies dancing on the golden grass. Tempted to enter the ring by the Fairy Prince's invitation to dance, she is saved by the iron nail in her pocket, iron being the only thing that can break fairy magic.