A most captivating time at Abashiri Prison Museum in Hokkaido
Access is either by walking (4km/40 minutes uphill) or taking a short bus ride from Abashiri Station. The bus doesn't run very frequently, but schedules can be found at the station. There's a restaurant that serves authentic prison food; I didn't get a chance to eat there but supposedly it's pretty good.
While in Abashiri, you can visit some other local museums or, in winter, take a drift ice cruise. Shiretoko is a short train ride away, a beautiful peninsula where you can take a nice cruise in the summer or walk on the ice in winter. That was my original plan, but the typhoon canceled my cruise. Due to the timing and duration of the peninsula cruises, they end up being a day trip or part of a multi-day stay in Shiretoko.
The museum was quite nice, and Abashiri/Shiretoko is worth a visit for the ice or peninsula cruises too. Note that it takes a long time to get to Abashiri from Sapporo by train and flights can be somewhat costly.