My city used to be an old coal mining town before the 1900's, so there are many mineshafts going through the underground of the downtown.
The mines stopped growing, but the town didn't, so the remote areas around the entrances soon became a suburban landscape.
The entrances were all blocked off, except one deep in the nearby mountain that is only wilderness for many kilometers. I live a one minute walk away from one of these blocked off entrances.
There are plenty of urban legends about these kinds of things, strange animals without hair, odd noises coming from the blocked off shafts, the like.

But I will say this, with absolute truth in my words;
There are many people dying here in the area around the mines, under odd circumstances. The bodies are always hidden away, tucked in a ditch, or in a hole, or between two places.
I've walked by many places, only to read in the news that there was a young womans body there for weeks, when I had obliviously stepped my way right through that same forested patch of land. A homeless man whose corpse had decayed for so long that it was difficult to identify him, found just behind a fence, with grass growing over him as if to hide him away. I walked by there every single day for months without knowing.

And I keep hearing screams at night. Always off in the distance, always from the same direction, but never from the same person... or thing.