Future London is the setting in which most of Professor Layton and the Unwound Future takes place. Though it shares some similar landmarks with present-day London, it is vastly different in terms of the conditions of its buildings. It appears that much of it is still under construction. It is accessed through the "time machine" that can be found in Spring and Cogg's Clock Shop.
It is revealed toward the end of the game that Future London is not actually the London of the future, and is instead a vast underground cavern built by Clive as part of his revenge plan for London. When the Mobile Fortress is awoken it breaks a hole in the "sky" of Future London. It is likely Future London was destroyed when the Fortress exploded inside of it.