The celebration of Midsummer's Eve was from ancient times linked to the summer solstice. People believed that at midsummer plants had miraculous and healing powers and they therefore picked them on this night. Bonfires were lit to protect against evil spirits which were believed to roam freely when the sun was turning southwards again. In later years, witches were also thought to be on their way to meetings with other evil powers.
In Sweden Midsummer celebration originates from the time before Christianity, it was celebrated as a sacrifice time in the sign of the fertility. The solstice itself has remained a special moment of the annual cycle of the year since neolithic times. The concentration of the observance is not on the day as we reckon it, commencing at midnight or at dawn, but the pre-Christian beginning of the day, which falls on the previous eve. Midsummer's Eve is in Sweden and Finland considered the greatest festival of the year, comparable only with Walpurgis Night, Christmas Eve, and New Year's Eve.