Wells are symbols of portals to the Underworld as well as to the realms of spirits and fairies. The water in a well was deep, therefore it was believed to have a direct connection to the Underworld. Wells thus were thought to be sacred and magical because of their association with spirits and deities. Often offerings were dropped into wells to appease the entities living beneath.
The well is also seen as a feminine principle, the womb of the Great Goddess. Therefore, its water is identified with the body fluids of the female. Women were thought to be magical because they bled every month without becoming ill or dying. The blood and vaginal lubricants associated with fertility were connected to life and considered magical. In correspondence the water from a well was believed to possess renewal and healing power.
In many regions of Europe the very old tradition of “dressing” well was popular as late as the 19th century. This tradition involved decorating wells with flowers, garland, statuary, and other items. This pagan custom was especially at Midsummer (see Sabbats) and represented the abundance of life born of Nature. The custom of dressing wells was eventually assimilated into the Catholic Church, and became associated with the Christian festivals centering on the themes of resurrection and ascension. A.G.H.
Source: 78, 391-392.