Today on a walk we spotted part of this, just visible from the walking path from one angle, walls that were part of an old foundation. So we climbed up for a closer look.
Some stone steps
You can walk right into the basement/lower level.
Nature will take over the walls but I'm not sure about that big hole in the ground 😮
You might never know it was there, especially as the foliage fills out. There was no trash in it so it doesn't appear that kids have found it. In the meantime, we'll check with the Ada Historical Society to see if they know anything about it. (Here is the view from the walking path.)