Gyokusendo Cave

This guide to Gyokusendo Cave in Okinawa traces how roughly four fifths of this limestone cave, carved by underground rivers over hundreds of thousands of years, has never been opened to a single visitor. It follows the 1967 university expedition that first pushed past what local farmers had only glimpsed, and the dense fields of stalactites so fragile that a loud noise can snap one from the ceiling. You'll hear why engineers kept the lit, railed section deliberately small. Keep your voice down as you walk it, since most of the cave stays sealed in the dark just past the barrier.