Then, inspired by NYC's High Line, Fletcher Priest won the Green Infrastructure Ideas Competition with his proposal for an underground mushroom tunnel beneath the streets of London.

ENGADGET: Inhabitat's Week in Green: Bicymple, computer-age fossils and an underground mushroom tunnel

And unlike the competition, Lot 258 in Allsop's residential sale later this month has two underground gaol cells.

BBC: Essex magistrate court to be sold in property auction