EnerGaia takes urban farming to a whole new level. The project transforms empty skyscraper rooftops in Bangkok into massive urban farms with dozens of barrels. The algae double in size every day thanks to the tropical temperatures Thailand’s capital. The green goo gets harvested three times a week, spun dried, packed by hand into jars and sold to shops and restaurants. The nicely designed jars of Skyline Spirulina cost around $14 each.