There's an underground grotto in the UK that's covered with millions of seashells -- and no one knows who made it

The Shell Grotto, located in Margate, Kent, in the UK, is a stunning underground grotto elaborately decorated with 4.6 million seashells.

Once you enter the subterranean world, you’ll be able to wander through 70 feet of winding passages that lead to a large rectangular chamber while gazing at the breathtaking mosaics of shells that line the walls.

Discovered more than 200 years ago, the Shell Grotto is surrounded in mystery as no one knows who made it or why it was built.

The legend goes that in 1835, a man named James Newlove happened to be digging with his son when a hole appeared. He lowered his son into the hole and when the boy emerged, he spoke of the elaborate tunnels.

A number of stories are told regarding its origin, with some saying it was once an ancient temple and others believing it was a secret meeting place for private sects.

The Grotto officially opened its doors to the public in 1838, with hundreds coming to the site to marvel at a location that had never been marked on any map, had never been discussed in tales, and had no sign of construction around the town.

The Shell Grotto is open to the public daily until November, and during weekends in the winter (Nov. to Feb.). Tickets cost about $US3.50 for adults and $US2.50 for children.

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