Wow what a cool sight! I've been out to Nagatoro and Chichibu and went on a riverboat ride and I think I remember the guy pushing the boat saying something about there being icicles there during the winter. I'd love to go back and see it sometime as this looks really amazing. Also we wanted to try the kayaking in Nagatoro as well since the water was too low when we went and the boat we rode on couldn't go as far downriver. I guess they have some skiing there as well, I'm not sure if it's connected to the ropeway at all, but that's another cool thing to do in the area. The mountain is really beautiful and I think there's probably a good amount of cherry blossoms if you go in the spring. I'd like to explore Chichibu more though as I hear there's a pilgrimage there where you can see temples and shrines and stuff.