Authorities in England have asked the public to help map Britain’s historic obsession with the paranormal by searching for markings on buildings that were once believed to ward off evil spirits. The ancient etchings were often carved near entrances to buildings, including Shakespeare’s birthplace in Stratford-upon-Avon, the Tower of London and Wookey Hole caves in Somerset.

During a time when belief in witchcraft and the supernatural was widespread, the symbols — also known as apotropaic marks — were believed to offer protection. The marks can be found on medieval houses, churches and other buildings, most commonly those built between 1550 and 1750, according to reports.

The marks are found in several forms, including flower-like designs, and sometimes include letters, such as AM for Ave Maria, M for Mary, or VV for Virgin of Virgins.

“More efficient oil lamps in the 19th century seem finally to have banished witches. We see them from the 16th century on, often in buildings already centuries old, but there could well be earlier and later marks that just haven’t been recorded," Nick Molyneux, Historic England’s historic buildings inspector said, according to the Guardian.

"Witches' marks are a physical reminder of how our ancestors saw the world. They really fire the imagination and can teach us about previously-held beliefs and common rituals," Duncan Wilson, chief executive of Historic England, said.

"Ritual marks were cut, scratched or carved into our ancestors' homes and churches in the hope of making the world a safer, less hostile place. They were such a common part of everyday life that they were unremarkable and because they are easy to overlook, the recorded evidence we hold about where they appear and what form they take is thin," Wilson said, according to the BBC.