This looks like a post card of the Priory Park Fountain from some time ago, when it was working and the trees around the park were but saplings. Do you have any photos from this era. If so please post them here or on the Volunteers Facebook Page
I've just added a new picture here on Harringay Online - not sure if it gives any more info than the one above though, but it's a nice addition to our 2,000 local historical images (with, as you'd expect, a Harringay bias!).