Shell Grotto, Margate
- For other examples see Shell Grotto.
The Shell Grotto is an ornate subterranean passageway in Margate, Kent. Almost all the surface area of the walls and roof is covered in mosaics created entirely of seashells, totalling about 2,000 square feet (190 m2) of mosaic, or 4.6 million shells. It was discovered in 1835 but its age remains unknown. The grotto is a Grade I listed building and is open to the public.
The Shell Grotto consists of a winding subterranean passageway, about 8 feet (2.4 m) high and 70 feet (21 m) in length, terminating in a rectangular room (the altar chamber) approximately 15 by 20 ft (5 by 6 m). Close to its half way point, the passageway divides to pass around a massive circular column called the rotunda. Attached to the grotto is a museum, gift shop, and cafe.
The purpose of the structure is unknown, and various theories have dated its construction to any time in the past 3,000 years, and speculated possibilities of the builders include the Knights Templar. The shells are all local; but some of the designs suggest associations with Phoenicia, and it has been speculated that the name of the Isle of Thanet, where Margate lies, may derive from the Phoenician goddess Tanit. The official guide suggests a subject for many of the mosaic panels, such as a skeleton, crocodile, owl, or turtle, but the abstract nature of the designs make these suggestions rather subjective.
The grotto was discovered in 1835 by James Newlove, who broke through into its roof while digging a duck-pond. It was illuminated by gas lamps and opened to the public in 1838, and has remained in private ownership ever since.
The age of the structure is uncertain and attempts to use radiocarbon dating to determine the age of the site have failed. Carbon deposits from Victorian lamps which were used to illuminate the grotto in the 1800s have entered the shells. Some of the mortar has so far defied analysis and all that scientists can ascertain is that it is fish-based. Mortar analysed from the easily accessible panels has been shown to represent a variety of mixtures, all dating from post 1796. It is a recorded fact, however, that souvenir hunters regularly removed shells from these panels in the nineteenth century and that they had to be replaced. This fact could explain certain results of these analyses. Indeed, there is evidence for a great deal of intervention in the site: a new archway was added in the nineteenth century  and certain sections (such as the so-called 'altar' panel and niche) have been dismantled and then restored since the discovery, as well as the original flooring having been removed.
The Victorian gas lighting has blackened the fragile surface of the once-colourful shells, which are also under attack from water penetration. It is now illuminated by electricity. During World War II the east wall of the so-called altar chamber was destroyed by a bomb.
- "The Name of the Isle of Thanet", Theo Vennemann, 2006, in Language and Text - Current Perspectives on English and Germanic Historical Linguistics and Philology ed. Johnston, von Mengden & Thim, Universitaetsverlag WINTER Heidelberg, pp.345-374
- Marsh, 2011, p.14
- Marsh, 2011, p.31
- The Enigma of the Margate Shell Grotto, Patricia Jane Marsh, Martyrs Field Publications, 2011, ISBN 978-0-9569437-0-5
- The Grotto, Howard Bridgewater, Fourth Edition, Truprint Litho Ltd, 1957
- The Shell Temple, Ruby Haslam, Regency Press, 1974
- The Subterranean Kingdom, Nigel Pennick, Turnstone, 1981, ISBN 0-85500-140-2
- Shell Houses and Grottoes, Hazelle Jackson, Shire Publications, 2001, ISBN 0-7478-0522-9