Take a walk in a nice quiet green. There's equipment for children and an adult exercise area as well.
You will need to keep an eye open for muggles, however.
While the immediate vicinity is wheelchair accessible, unfortunately the cache itself is not.
You are looking for a camouflaged item. (Added as people seem to be finding this one surprisingly hard.)
I've had to replace the original with something completely different. Please be careful removing it and try to put it back as you found it. Thanks.
urnq urvtug vfu. Qba'g zvff gur jbbq sbe gur gerrf.