Zenkoji Temple was high on our list for Nagano but we didn't make it - though it sounds like one of those can't-believe-it's-not-more-famous spots. I mean, it's THE temple that houses Japan's first-ever Buddhist statue! That's serious historical cred right there.
The part that really caught my attention was this underground passage where you're supposed to feel around in complete darkness for the "key to paradise." Love how Japanese temples aren't afraid to get a little mysterious and mystical. Plus, you can actually stay overnight in temple lodgings, a la Koyasan, which sounds like one of those bucket-list Japanese experiences.
For a temple that's been around since the 7th century and holds such an important piece of Japanese Buddhist history, it's kind of surprising it's not as hyped as some of Kyoto's temples. If any of you make it there before we do on our next trip, I'd love to hear if you found that key to paradise in the dark!