I came to Greece a bit blasé about caves. We've done Waitomo (in NZ), which is pretty nice, with some fine glow worms, and we visited several in Cuba - some where you could swim spookily in the dark underground caverns. So when we walked down to the Dirou Caves one afternoon and found them closed, I wasn 't too bothered. How wrong I was.
If I hadn't been persuaded to persevere the next day, I would have missed out on a rare treat. The Pirgos Dirou sea caves are quite amazing. More than a kilometre of well-lit caverns, joined by narrow tunnels, which you explore in a small boat. It's not hard to imagine Charon, the mythical boatman who ferried half-dead souls to Hades (the underworld), in exchange for a one obol coin.
More prosaically, you get almost an hour of jaw-dropping rock formations and staggering reflections. If you are ever in the Mani, it's a must-see.
We knew the cave at Tainaron, at the bottom of Greece, wouldn't be quite so spectacular, but still, it has a good legend behind it. Myth suggests it is the entrance to Hades, used by Hercules when he went to catch the three-headed dog Cerberus, guardian of the underworld. As an aside, Cerberus was the inspiration for JK Rowling's "Fluffy", the three-headed dog that Hagrid got from a Greek man he met in a pub, and which guarded the Philosopher's Stone. Fluffy, like Cerberus, had a fatal flaw (in terms of his usefulness as a guard dog) - music made him fall asleep.
With that as a backstory we made the detour to the cave. Big disappointment. I don't know what it was like when the Ancients roamed, but these days it's not even a proper cave - just a bit of an overhang littered with dodgy-looking bits of toilet paper. Don't bother.