AKIYOSHIDO, Japan — May 19, 2025 — On a warm, muggy day, we welcomed the cool air and green, limestone-infused river gushing out of Akiyoshi Cave, the largest and most impressive limestone cavern in Asia. The cave cuts almost two kilometers into the rugged landscape of the Akiyoshi Plateau, a karst landscape created over 300 million years and now preserved as a Japanese national park but which looks more like something out of rural Ireland. The aging tourist facilities (charmingly Showa-era says Courtenay) and run-down retail strips around the massive cave disguise a really remarkable natural wonder.