In the '60s and '70s, Paris built underground parking garages for just about every large apartment complex in the city. Now that car ownership is in decline due to rideshare apps and other technology, these garages are being abandoned. A company called Cycloponics recognized the large, dark, dank spaces as ideal conditions to grow one of their favorite crops and set out to create organic mushroom farms. They've taken over three garages so far, with oyster, shiitake, and white button mushrooms being grown, harvested, and sold directly to local organic markets.
See the farm in action in this video from the BBC.