Royston cave is a small artificial cave in Royston in Hertfordshire, England. It has been speculated that it was used by the Knights Templar, who founded nearby Baldock, but this is inherently unlikely, despite its enormous popular appeal. It is more likely that it originated as a cell for anchorites from the nearby Augustinian Priory, although a recent suggestion is that it was the town's earliest prison, perhaps dating from the late fifteenth century. It is open to the public in the summer months on Saturday, Sunday and Bank Holiday afternoons between Easter and October.