an area of a large city where many people without a home sleep outside.
Young people come to the capital full of hope and end up in cardboard city.
cardboard city
noun a prison segregation unit. Derives from the fact that the furniture in such prison cells is often made from cardboard UK, 1996
cardboard city
An area heavily populated by homeless people (who sometimes use cardboard for warmth or makeshift shelter). Our local government does little to help the cardboard city, and it just keeps growing in size.