Wastes

The British have a useful word to describe marginal spaces; wastes.

I don't know that the American vocabulary has a synonym. We can describe vacant lots, abandoned houses, road margins, empty fields, levees, parks, and such, but not all of them with one word.

The utility of the word is that it neatly sums up both the perception and the  promise of underused spaces. In the eyes of a person having trouble finding affordable housing, the levees, abandoned lots,  and road medians of your typical urban environment are both wasted spaces and ripe with promise.