Went to a camping in the Laurentians in Québec (Ste-Agathe) and there were those things near some camp sites. The sites are only accessible by footpaths. No car access. And if you bring a bike, you have to walk it up a hill, so I doubt they are bike racks.
EDIT: I have sent an email to the park and they have been kind enough to reply. It's just a type of fireplace with a grate. They didn't give more info than just this. Thanks to everyone for pitching in!
I'm surprised that no one has said "concrete anchor for an unfinished building structure". Doesn't this look like someone laid the foundation for a tower or building or something with the concrete anchor underground, and this is a tie-in area for the additional rebar structure of either a column or a wall that could have joined here? The metal configuration here looks a lot like what's inside concrete pillars but we usually don't see it