Hampstead Heath
After seeing this foliage map of the US (via kottke.org), I was initially a bit jealous.
Until I read this article encouraging Americans to visit London. Why? To see the view from the London Eye? To shop at Harrods? Nope. To see the fall foliage on Hampstead Heath.
I've mentioned Hampstead Heath recently and taken few photos there. It really is one of my favorite parks of all time, and it's just a ten minute walk from my office. With any luck, I'll take some photos of that spectacular foliage this fall.
It's also one of the few parks I know of with an active twitter account. Apparently, Hampstead Heath's catch phrase is "Heath love for all."