2 years ago we went to Noboribetsu (登別) and stayed 2 nights at Dai-ichi Takimotokan (第一瀧本館). We stayed in a Japanese room and really enjoyed it. We chose the package where they serve a traditional Japanese dinner in ourroom, and we (including my son) really enjoyed it. It is a really good cultural experience.
There are many sight-seeing locations near by. We went to Hell's Valley (地獄谷), Bear Park, etc. We went to the hotel's hot springs several time because it was really specail. It was really good, except you have to get used to walking around naked. But taking a hot springs bath outdoors with snow around you is really relaxing!
I didn't know it is 登別最豪的一間! It was recommended by a friend who is an air stewardess with Cathay. She reminded me to stay there if I go to 登別. But I don't think it was so expensive. I think we paid around 30,000 Yen for a Japanese room (tatami) including in-room dinner.