'Jungle' has come through common Western usage to mean a densely overgrown, humid tropical forest, where danger and discomfort lurk. Its Sanskrit root jangala simply means 'uncultivated land'.
Jungle and city are mutually inimical places: one is civilized, the other wild.
In two seminal literary works of the early 20th Century, Upton Sinclair's novel, "The Jungle", and Bertolt Brecht's stage play, "In the Jungle of Cities" (hence, my title), the jungle is a metaphor for Darwinian savagery among men in the supposedly civilized setting.
Hobos once referred to gathering places hidden among vegetation near railroad stops as "jungles", where they could rest in between journeys; places where railroad cops and other agents of civilization did not habitually stray.
There also exist many wild and semi-wild places in and around a city, some surprisingly extensive, most vanishingly small. Places not yet claimed by the encroaching city, reclaimed by the encroaching forest, and in-between. These 'jungles' are my putative subject – along with urban parks and suburban tree canopies which may present a jungle-like aspect.
Maybe some of these were or are used by homeless people as their jungles. I've stumbled upon a few disheveled camps (though rarely their inhabitants), in my perambulations.
Many/most of the subjects here don't really qualify as 'jungles', except in my imagination.
I expect they will eventually either become more like jungles, a desert, or each in turn.