I spotted Ishiyama Park on the Sapporo government website back when Bunny was staying with me. It looked kind a like a modernist colosseum... as a park in Sapporo? Thus I really wanted to go there, and finally got my wish last week.
It's not too far south of Makomanai, but it is easier to get there by car than by any other means (oh! maybe horse would be convenient?) and it's not really marked very well on any maps. In fact, despite the epic scale of the stone installations above, it actually feels like a pretty small community park. Though living in a community with that stuff in your park would rock like Beethoven in Bill and Ted's Excellent Adventure.