Wiktionary
n. An area of a town where the homeless gather at night to shelter under makeshift constructions of discarded boxes and packing material.
Wikipedia
Cardboard city ( Serbian: Картон сити, Karton siti) was an informal settlement, or locally classified as unhygienic settlement, basically a slum in the capital of Serbia. It was located in Belgrade's municipality of Novi Beograd. The settlement was completely evicted and cleared in 2009.
Cardboard City was the name for an area of cardboard boxes near Waterloo station in London, England, lived in by homeless people from 1983 until 1998.
In the mid-1980s the site, in the pedestrian underpasses under the Bullring roundabout, was home to up to 200 people sleeping in cardboard boxes. By early 1998, fewer than 30 people remained there. These were officially evicted by the London Borough of Lambeth in February 1998, and forced to leave before the end of March 1998. All were offered free housing by the Borough, although there was concern as to whether the residents would be able to cope with housed life. The area is now the site of the London IMAX cinema.
The main character of Rebuilding Coventry by Sue Townsend lived in Cardboard City for a time.
The song "Cardboard Box City" by The Levellers (on their first album A Weapon Called the Word from 1990) is about this site and most people's ignorance towards those social living conditions.
Usage examples of "cardboard city".
It is a dark business, Yaivazaki thinks and wonders, taking the stairs to the cardboard city, what exactly Laney is about here.
There wasn't a cardboard city north or south of the river where he wasn't known, and prayers said in the hope that he'd not come visiting.
He was young and fresh out here from Jamaica or Haiti, recruited from some cardboard city on a mudbank by an entrepreneur with a gold watch and a diamond pin and stories of fortunes to be made, hey big daddy here I come, and I didn't want to spoil everything for him but it would have to come to that.