After an 8-kilometre riverboat journey up the Urauchi-gawa — Iriomote's largest river, snaking through dense subtropical jungle — you'll dock and walk 2 kilometres through the forest to reach Mariyudu Falls. The waterfall tumbles in a wide, tiered cascade into a jungle pool, and the combination of the boat ride and forest walk makes the reveal genuinely dramatic. Another 200 metres beyond lies a second waterfall, Kanpire-no-taki, so you'll get a two-for-one reward for the effort. The whole experience feels like an expedition into Japan's last true wilderness.