Longyou Grotto is a magical archaeological nugget in Longyou County, China. The grotto consists of at least 24 huge caves all hand carved into the solid rock. But no one knows who made them, why or how. At least a million cubic metres of stone were removed to make these bad boys, which is no small feat in the days before TNT. Unfortunately no written record of who made them or why has yet been found.

The Longyou Grotto is considered by the Chinese to be the ‘Ninth Wonder of the Ancient World’ and one of the biggest subterranean excavations of ancient times. Amazingly they weren’t discovered until the 1990s. I say ‘amazingly’, but I suppose if you aren’t looking for huge underground caverns you won’t find any, will you?

So how were they unearthed? I’ll tell you: The villagers of Xiaonanhai region lived happily at the bottom of a hill and had done for many years. After a spate of particularly bad floods they were forced to move their homes up to the top of the hill. At their new home-base they found a number of pools of water which the inhabitants found useful for drinking and cleaning and all that normal watery jazz.

These pools never dried up and when they tried to measure their depth with bamboo they couldn’t reach the bottom. This mystery proved too much for a local chap, Wu Anai, and he decided to drain one to see what was going on. He didn’t find what he expected at all.

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