ウェルネスパーク五色
This complex in Tsushi, in Goshiki, houses a number of facilities, including a public park, a hotel, an onsen, a campground, and a museum. The museum is dedicated to Takadaya Kahei, a merchant sailor who played in important role in the development of Hokkaido during the Edo Period, and who was born and raised in Goshiki.
Tsushi is easy to reach, with direct buses from Kobe (some of which travel to the Wellness Park itself), as well as a few local buses.
The museum costs ¥500. There is a website in Japanese: