A 70-Foot Subterranean Cavern Adorned With Millions Of Seashells

From Great Big Story, this fantastic (and mysterious) little tidbit:

Less than six feet beneath a residential neighborhood in the English seaside town of Margate lies a mysterious underground cavern. Nicknamed Shell Grotto, the subterranean passages wind for 70 feet and are adorned by millions of seashells. Who built the cavern and for what purpose remain a mystery.

The relentlessly-reliable Wikipedia says that "the purpose of the structure is unknown, and various hypotheses have dated its construction to any time in the past 3,000 years. Hypotheses include: it was an 18th or 19th-century rich man’s folly; it was a prehistoric astronomical calendar; it is connected with the Knights Templar or Freemasonry."

Personally, if this discovery does not involve Indiana Jones in some way, I'll consider it a huge missed opportunity.

Attribution(s): "Shell Grotto" by Gernot Keller is made available via a Creative Commons license (CC BY-SA 2.5) and shared through Wikipedia.