We really wanted to see Ryusendo Cave but didn't make it far enough north into Iwate Prefecture. This place is a gem for anyone into natural wonders; it's a limestone cave system with underground rivers and lakes that seem almost otherworldly. The water here is so clear and blue, it's like nature's own aquarium.

Walking through on raised pathways, you get to marvel at the rock formations and perhaps catch a glimpse of the resident bats. It does require a bit of legwork with stairs, making it an adventure in itself. Missing out on this spectacle was a bummer, but it's definitely on the list for next time.