Trampoline built into yard

Anyone ever encountered a trampoline set into concrete in a yard before?
I just wrote it up with the standard “not inspected, may pose a hazard” but didn’t have much else to say.

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A friend of mine did that for his kids. He hand dug the pit and set the trampoline in. He didn’t set it in concrete. I believe he partially back-filled with sand.

If you’re going to land on your head, it nice not to have that extra 3 feet to fall.