Incredible grotto made of shells has stumped historians for centuries

The Shell Grotto in Margate is built with over four million shells, but experts are stumped as to how old it is or why it was built

A unique visitor attraction has been puzzling historians for hundreds of years, with its age and purpose remaining a complete mystery.

The Shell Grotto in Margate, Kent, consists of an eerie underground passageway called the Serpentine Passage that leads to a room known as the Altar Chamber, and is described as a “storehouse for the imagination”.

The curved walls are encrusted in more than four and a half million shells, with ancient cockles, mussels and oysters forming mysterious patterns that make for a stunning sight for tourists to behold – but offer little clue as to the grotto’s original purpose.

Ever since the grotto was first opened as a tourist attraction in 1838 soon after it was discovered by accident, there has been fierce debate around when and why it was first built in the first place.

Some believe that it was constructed as a rich man’s folly at some point during the 1700s, when extravagant statement displays like this from wealthy travellers were popular.

However, others believe that the grotto is in fact much older, with other theories dating back three thousand years that suggest it’s an ancient place of worship or an astronomical calendar.

There are even conflicting accounts of how the grotto was first came to be discovered. The earliest record of the mysterious structure dates back to 1838, when it was first opened up to the public.

The announcement was made in the Kentish Gazette that the grotto had been found by workmen while excavating to carry out renovations on a cottage. The article describes the grotto as “one of the most curious and interesting sights that can possibly be conceived”.

However, it’s widely believed that a teenage boy called Joshua Newlove was actually the first to discover the grotto around 1835. A story from his younger sister, Frances, is the best surviving account of the remarkable find – and in it Frances claims that she and her brother kept the grotto a secret for years.

“My brother found out about the underground place sometime before it was known. He never dared to tell father,” Frances, who was around 12 years old at the time of the discovery, wrote.

“He crawled through and got into the grotto. And so did I. Yes, and two or three other young girls too. […] We got in and saw it all; we had to take a candle in a lantern round somebody’s neck.”

While the grotto’s exact age and purpose remains a mystery, efforts are now focused on helping to conserve the Grade I-listed building. A group began the painstaking task of preserving the grotto in 2007, replacing loose and damaged shells.