Several schools I know of have part of their playing fields on reclaimed land that's former landfill. You can't build on it because you have no idea what sort of gases and possibly toxins will work their way up from below, but wide open fields with free air movement that aren't round-the-clock occupied are fine. The only downside is that for an initial period you need to re-cap places with soil every few years as the fill underneath settles. There was one place where they'd paved over it rather than leaving it as soil to create tennis courts and after a few years it was a sort of dune landscape since they couldn't backfill the dips with soil. It was quite picturesque actually, a sort of post-apocalyptic look with miniature ponds with reeds growing in them and occasional visits from ducks. Sure, they'd lose a kid in one from time to time, but being a large school they didn't have a shortage of those.

This shopping center was built on a landfill

https://www.wskg.org/regional-news/2025-08-08/binghamton-off...

when I first saw it in the 1990s it was kinda on the outs, like K-Mart was already failing (as a business) and the parking lot was visibly wavy because of subsidence. Funny the New York Pizzeria mentioned in that article is run by my relatives.