Onigashima Cave

Megijima is twenty minutes off Takamatsu, and near the top of it is a cave system running about four hundred metres into the hill — chambers, passages, a throne room — cut by hand at some point in the distant past for reasons nobody has established. In 1914 a local schoolteacher rediscovered it and proposed that this was the demons' island of the Momotaro story, and the island has run with it ever since.

The archaeology is genuinely unresolved; the demon figures inside are twentieth-century additions. What is not in doubt is that somebody dug four hundred metres of passage into a hill on a small island. Entry is ¥600 and a bus meets the ferry for ¥100 each way, taking about ten minutes up the hill. The summit above has a view over the whole Inland Sea.