Around 1995, when I was around 11 or so, I read a story as part of a reading program at the Hennepin County public library in Maple Grove, Minnesota. The following has stayed with me:

• The main characters are children, probably around 12. They encounter a wall (perhaps a dense hedge) in a woodland near their town. The existence of the wall may be surprise to them, but if not, they know that it is prohibited.
• One or more kids find a way over the barrier. There is some cause for concern (perhaps the trespassers go silent or else simply have trouble getting back over).
• During the resolution of the story we learn that the wall/hedge encircles an area that the town had closed-off a generation before. (I envision this area as a garden on a hilltop, but this vision of the landscape may not be grounded in the text.)
• The children’s parents join them in the isolated area, and rather than being angry with the children for trespassing, they tell the tragic story of why the area was closed. Ultimately the older generation finds some peace from the process of sharing the story and remembering a part of their youth that had been forgotten.

I think the kids had bicycles, but nothing about the story felt particularly immediate, so the publication window could be 1950–1995. I don’t recall there being any pictures, and I think the total reading time was on the order of an hour.