Manuel Dominguez’s "Very Large Structure" concept dreams of nomadic cities that aren't abandoned when local resources are depleted or due to economic shifts. Instead, the cities would pick up and find a new home, allowing for the reforestation of the places they leave behind.
The notion of a mobile city is, in itself, nothing new; Ron Herron of Archigram envisioned his walking city back in the 1960s. And Dominguez acknowledges that there isn't much of a demand for mobile cities (which come with a host of issues themselves). But as his thesis project at ETSA Madrid, he wanted to build out the concept of a movable city and understand how it might operate on a practical level. There are impressively detailed presentation slides at Petropia and ArchDaily (written in Spanish), delving deeply into the construction of his Very Large Structure.
The concept calls for the 600-foot-tall city to move on configurable tank wheels, and to function off-grid. Solar panels would track the movement of the sun and turbines would capture wind power. The city would house residences, hospitals, school, libraries, and other amenities you would expect in a self-sufficient city. Airship docks and helicopter pads would enable transport onto the high platform. It may not be the most practical idea for the modern era, but it's an interesting proposal for countering the problem of abandoned cities and the waste left in their former inhabitants' wake.
Top image created by Poliedro.