Royston Cave is a unique man-made cave located in Royston, Hertfordshire, England. Discovered in 1742, it is carved from chalk and features intricate carvings that date back to the 12th century. The cave is believed to have been used for religious purposes, possibly linked to the Knights Templar. The cave measures about 30 feet long and 15 feet wide, with a high ceiling. Its walls are adorned with various symbols and figures, including crosses and other religious imagery. Today, Royston Cave is a scheduled ancient monument and is open to the public for guided tours.