Hot Springs Park

This guide to the Hot Springs Park west of Da Nang starts with an odd puzzle: nine holes drilled into the same volcanic rock, only meters apart, yet each surfaces water at a different temperature. You'll hear what it took to tame that mismatch into safe soaking pools, including the Japanese onsen consultants brought in when the park opened in 2016. The water gets noticeably warmer the further back into the park you walk, drawn from a hotter branch of the same underground vein.