We live in an apartment, in the city. No backyard, no front yard, and "No dogs Allowed on Grass" anywhere here. Which is ridiculous because my whole neighborhood is one big "park". Hence the name, "Battery Park City".
Anyway, the only way he can get any real exercise is by going to the dog park. We can take off his leash, he gets to run around and socialize (or hump his favorite Pittie girlfriend).
Lucky for us, there's usually great people at the dog runs here. Plus, we get to choose from three, all within a few blocks of where we live. What sucks is all three parks are concrete. No grass or trees. The one closest to us does have a pool so our pups can keep cool in the summer, but that's about it.