Hmm. Possibly to place gathered firewood so it doesn't get under foot?

looks like a grill to me.

it holds firewood (but not right now)

Vertical Rack for storing clay tool molds. Keep an eye out for a friendly seraph. They're clearly in the iron age at this point.

Does a typical cooler for under that?

Is there cross country skiing there in the winter?

This is to make sure your carry on fits on the trail (jk)

Is the area prone to bears? Could be the remnants of a small bear box for a cooler or something that went over it, either some sort of information kiosk or storage/waste box that's no longer there.

Nice steady pic. Especially with sasquatch looking on... waiting to tie his mule up before taking a dip in the stream?

Oh you can put your weed in it

Could it just be a deteriorated bench?

Maybe cross-post to Canada@lemmy.ca ? And update us if you get an answer!

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

Horse hitch?

My guess would be a very uncomfortable bench.

Either a bike rack or a really shitty barbeque grill.

OP, none of the answers here are satisfactory. Please ask the rangers and update this post because this is fascinating.

Google Lens wasn't helpful, it compares it to things like drains and fences built around old markers (it specifically thought it was a Mason-Dixon line marker which is obviously incorrect). But this is not protecting anything and not a drain.

My guess is, if it's not something to tie a horse to, is maybe it's something to put animal feed in? But that's a wild guess, I don't really think it's right. Like shove a hay bake in. But you said only accessible by walking, so I really doubt it.

This is clearly a rack to store your slates with commandments.

I'd assume it's for wood if there are designated fire areas for each camp. I could see it being even more useful for wet wood, allowing you to set it near the fire to dry out.

bike rack

My bet is it's for drying wood, but the design isn't quite there for that. It's possible they constructed it in place

Maybe something related to an old logging or mining operation. Could be a protective cage for some equipment.

My guess is that they were moved there from somewhere else. They were maybe used as grates to strain debris from the water, or some kind of heat exchanger. That area was definitely made flat with heavy equipment at some point.

Maybe some kind of bear-proof storage? Like maybe it would have gotten some plywood on either side seasonally?

Maybe a way to keep bears from getting into a cooler? It would need some way of closing the sides but maybe that piece is missing?

Maybe it's a grate. Imagine having a concrete pipe extend to both directions, this could then act as a grate against larger objects into the pipe.

The important question is how did it get there? That thing is going to weigh a ton (metric, as it's in Canada) and if you can't scoot it up there in a vehicle, then that's a logistical problem all in itself.

Giant toast rack

There doesn't seem to be anything culturally significant under the bars, perhaps because it was removed via the open sides.

Dry place to set your backpack in wet weather?

Maybe you put a canoe on there somehow?

Looks like a grill design to me.

Roughly how big is it? I feel like my sense of scale might be a bit off.

But some thoughts based on how big I think it is.

The bars look too far apart to be useful as a grill, also a little awkwardly low to the ground for that, not that campers are overall opposed to squatting or sitting on the ground if it comes to it, you could maybe put pots, pans, griddles, etc on it above a fire, but I don't see any evidence of the concrete being discolored from that.

The bars also look too close together for it to be a bike rack, and the little bars going across it seem like they'd be kind of inconvenient for that purpose.

You could maybe put a cooler in it, it wouldn't be particularly useful for protecting it from bears with the open sides, but could maybe keep a raccoon or something from getting the lid open, or if you bring a cable lock it might be effective at keeping bipedal scavengers from walking off with your cooler or stealing your beer.

Also seems a bit low to be a hitching post for horses or whatever.

As far as being a firewood rack, it seems a bit small for that, but I guess if you're not as big of a pyro as me and all the former boy scouts I know are then maybe its sufficient for that purpose.

The answer that makes the most sense to me is that it's for skis, or maybe trekking poles or something like that. Lets you store them upright so they don't get stepped on or buried in snow, leaves, etc. you said that the sites are closed in the winter, which puts a dent in that theory, but was that always the case? The concrete is a bit busted-up, so they've probably been there a while, maybe years ago they allowed winter camping and a lot of skiers used the sites. Also would explain why some sites have them and others don't, if they don't allow winter camping anymore, it doesn't make sense to replace the ski racks when they're damaged or to install them in newer sites.

Shoe rack I reckon

Where is the news on this one?!

My guess is either a seat, something left over from an eagle scout project, or a cooling rack. Somewhere to put your hot pans/utensils to let them cool/serve from without putting them straight on the forest floor.

Like a lot of things in camping though, it's probably whatever you make of it. Improvise and have fun.