Vertical farms have been touted as a way to feed a rapidly urbanizing world population (I've waxed poetic about them myself.) Critics of the trending technology, however, contend that these energy-intensive hubs are too costly and perhaps impractical to maintain.

Sure, the naysayers have a point, but what if vertical farms did more than just feed mouths? In Stockholm, Sweden, the Plantagon CityFarm located in the basement of the iconic DN-Skrapan building in the Kungsholmen district has a whole other purpose besides nourishing the office workers on site—the farm also recycles its heat to warm the offices above.