Every year on the feast day of St. Walpurga, hordes of revellers in witches' costumes gather on the summit of Mount Brocken in the Harz mountains to celebrate Walpurgis Night. This traditional German festival, an extravaganza of broomsticks and dancing, now attracts people from all over the country. Why not join the thousands of would-be witches on the night preceding the first of May and turn back the clock to the Middle Ages?