Let me introduce you to the "alternative green lung" of London, a solidarity-based botanical garden that serves as a café. And as icing on the cake, I'll write about my personal challenge to reach London on a budget and on a minimal luggage.
All the cities I recently went to, the places I enjoyed most, were projects that were initiated by neighbors, designed for everyone's participation to make the neighborhood more livable. A project like this is Klunkerkranich in Berlin. Apart from cultural events and urban gardening, the best thing is the view over the city including the TV tower!