I originally considered playground hunting to be "maintenance hunting" where I could always find enough change to keep me in battery and lunch money.
But since I find far more gold there than on any beach or grassy area, it is now a weekly ritual. The benefit is the area is more compact. Go there early in the morning, make sure you beat the local competition. And do 7 to 10 of them in short order.
Woodchips- Bad for the Saca dolls but fine for other coins, keeps them fairly clean and easy to find, downside is lots of nails and cans get ground up with those chips so it will be a while cleaning out a first fill or refill in a playground.
Sand- Same as most non-saltwater beaches, pretty easy to detect and find except for the hairpins, grommets and small button snaps that go through sifters but sound good.
Pea gravel- Wow! Got about 200 dimes out of one dime-toss from a carnie site in pea graqvel once. I swear you could not see the dimes in as they blended very well into the white gravel. Don't like the gravel because it damages jewelry quickly, but don't discount it.
Playgrounds are one of my favorite places to hunt when I am not looking for older finds, relic or coin. I've got the gold to prove it.
Best spots, baby swings. Early spring & late fall moms drop rings and bracelets when removing gloves to play with baby. For some reason other people believe their kids must wear gold and this inevitably ends up in the playground.
I am two monogram rings away from spelling out my daughter's first and last name with these rings and she keeps insisting I just go buy them to fill out the set, sorry, I know we'll find a "Z" and a "L" one of these days I tell her.