Space is at such a premium in London so we appreciate even the tiniest amount of outdoor space. My flat is on the first floor and outdoor space is limited to a narrow parapet at the front and a set of (external) steps at the back.
At the top of these steps is three square feet of space which I've tried to maximise, along with the space on the steps. It's north facing, so a sun trap in the late afternoon but the sun also reaches there in the morning.
This year, for the first time, I have grown vegetables: rocket (arugula), lettuces, spinach, tomatoes, as well as the usual herbs that I grow every year. I dug out an old mirror from the loft and metal table and painted them in Annie Sloan paint to add character and bought an old French painted folding seat which slots in perfectly. I keep the seat on a hook in the kitchen when not in use. It's amazing what you can condense into a tiny space and still create the effect of space.