"Where is this?" sounds like an interesting part of a community, but I'm having trouble imagining a community forming around just that.
More specifically, I could see this being part of a general puzzles community, or as part of a travel community, or -- with restricted scope -- part of Outdoors. In all of these cases, you would have a community of people who have already gathered for a broader reason, into which this kind of activity fits much the same way that challenges fit on other communities. (Several of our communities have weekly, monthly, or intermittent challenges related to their scopes.) Or, if there were a community for puzzles, this would sit alongside other puzzles that people post.
(I'm aware that Somewhere Else had a puzzles site, but I wasn't active in it and don't know much about it.)
I encourage you to add this aspect to a broader proposal, where I think it would be much more successful.