The Shell Grotto is an underground passageway covered with seashells and it was accidentaly discovered in 1835 in Kent, England. Its exact purpose and origins are still unknown. It might be a place of worship, a meeting place for a secret sect, or a folly of a rich person. The patterns of the mosaics are also open to interpretation. There are, for example, trees of life, phalluses, gods, goddesses and something that looks like an altar. The exact date of construction is unknown as well although some guess that it is 3000 years old. The shells have not been carbon dated yet as its private owners need to provide a number of samples and the cost it high. So, they focus more on the preservation part for now.