After our Jingisukan lunch we had already planned to go for a relaxing bath in the onsen constructed inside the same building as the restaurant. As there was nobody else there in the men's bath I managed to get some photos of the bathing and changing areas. It's a very small onsen with just a single bath - and no outside bath despite initially looking like there might be - but there was a nice view from the window.
 
The place is called Sagirisou (さぎり荘) in Shinshushinmachi (信州新町), which is about 30 minutes south-west of Nagano city by car. It was a great day out in all, and the weather was pleasantly cool.