What do you do with an old car park that no-one wants to park in? Why not use them to grow mushrooms - or even salad?
Paris built too many underground car parks in the 1960s and 70s. Falling car ownership means many are standing empty, or finding new and surprising uses.
The BBC has carried out a special report on the city that's re-purposing old car parks and turning them into modern day mushroom farms.
Watch the full video report here.