How do I get this? The achievement says to "Complete the tour of Riverside". I thought that maybe meant that I had to click on the trees to the right and do the nature hike but that did nothing, unless I'm missing something in there (I've moused-over everything). Then I clicked on everything in Riverside to try and cover everything but still nothing.

I know I can just buy the achievement prize but I'm cheap and I'd like the achievement as well.

I'm not sure if this is still active or not.

But to get the achievement, you had to do the walk, but also spot all the hidden items, as per the list on each page. If you've done that, and don't have the achievement, I would submit a ticket. It might glitched, or they might tell you it isn't active anymore.