The best of which, in my view, is the pre-school centre in Telegraph Hill. It's a pretty innocuous building beside the play area for young kids in Telegraph Hill's lower park (the black blob on the map above). If you've only visited the park on a weekend, you may have assumed, like I did, that it was some kind of storage shed, thanks to its dark shuttered windows and lack of signage.
I was led to it one day by my son, who spotted an array of plastic cars to play with, outside its front door. The cars led like a trail of sweeties, inside the building, which turned out to be a lovely play centre, as relaxing as any room full of toddlers fighting over a pretend microwave oven can be.
I think it's a degree nicer than St. Andrew's, particularly given its beautiful setting. The park itself was reopened in 2005 and boasts the best slide this side of Tate Modern.
Opening hours are 9.30 - 3.30pm Monday - Friday.