The city I live in (Buenos Aires) is actually very walkable, but there are some problems with the sidewalks, where sometimes they are too slim and in some places, the tiles are broken and accumulate water from the rains. There are also some intersections that lack adequate zebra crossings, and some parts of the city don't have good tree coverage (for there are no trees on the sidewalks or they are too small to give shadow).
A city thought for favouring people who walk over people that use their cars when moving around is definitely one that takes into account sidewalks, coverage from the sun and other elements and street crossings. My city provides a lot of this, but there's still some room for improvement.