When atara and I were driving home from dinner the other day, we rounded a bend in the road a few blocks from home when I pointed at something hunkered down under a truck parked along the side of the road and said, "What is... that?"
atara stopped the car and we stared at the little critter for several seconds while it stared back at us. At first I had thought that it was a fox, then we agreed that it moved more like a weasel. We drove a bit further up the street and then pulled over and parked so that we could get a better look. As we were walking back, it bolted out from under the truck and then scampered up a nearby elm tree with practised ease. Definitely not a fox.
It was early evening, and between the mediocre lighting and the fact that the creature was darting around nervously, I was having mixed luck trying to get a picture. Eventually it left its perch in the elm tree and scampered across the road where it took up a roost in an evergreen outside of somebody's house. That's where I got this (slightly blurry) shot. It's not perfect, but it was the best picture of the lot.
By the time we got home, atara was pretty certain that it was a marten, and some quick checking on Wikipedia bore that out. It is pretty obvious that it is not a fox in these pictures, but unmoving, in the shadow under that truck, it bore a striking resemblance.
I have never seen one of these in the wild, let alone in the city. If I know nothing else about martens, I can say from first-hand experience that they are almost dangerously cute.