We can somehow agree on the fact that the figure-ground diagrams are a first approach to the description of the urban space. But this leads to the need to define at which level you cut the urban shapes. For instance, let’s take Madrid cadastral map: the firs image shows the private lots (or those whose use is not entirely open, as it includes some public properties). This, in the end, renders the public rights of way of all kinds.
If you erase all the spaces that have no visible buildings (including those that only have underground constructions), things change a lot. Most of the courtyards, parking and similar things disappear. It is what you usually see in these maps.
But we can go further, taking just elements whose height is above a certain level. Here, just those over 8 storeys. And the city becomes a different thing, with some logics more apparent, but other situations being less clear.