I got the premium package at the Dōgo Onsen, allowed access to both bathing facilities, access to a small museum, and a tour of the emperor's own facilities. Then, at the last room, I peeked out. Photo's inside are permitted, but seriously, you'll have to come here and see for yourself. It's that good.
taken on 20 April 2015, 20:14
location: Dōgo Onsen in Matsuyama, Ehime, Japan