&gt; The larger the city, the higher is the likelihood of public spaces having a variety of homeless encampments, broken glass, needles and plain old feces.<p>The larger the city, the higher is the likelihood of accessible but nevertheless private property having those same things; though in either case its likely to be restricted to particular parts of the city, and those are likely to be the ones with lower property values (this reduced property value is both a cause and effect of the condition, its a positive feedback loop.)<p>The larger the city, <i>also</i> the more likely public -- and accessible private -- spaces are to be fairly pristine enclaves. These will usually be found in substantially <i>different</i> parts of the city than the nasty bits.