This looks like it was the entrance to a large pen. A fence stretched out behind it left and right, maybe wolves, large birds or something else around this size made it's home in here.
This large blue container looks as if it held maybe ducks or beavers at one time.
Closer inspection shows a large concrete object that has a slide carved out in it and some stepping stones.
Ducks and waterfoul or even beavers might have been kept in this area, the log wall is still here against the water but all the other area around this is overgrown.
This appeared to be a stage at one time. The clearing before it has thinner, newer trees that wouldn't have been around 30 years ago.
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