Lima, Peru, gets about half an inch of rainfall per year. Yet the atmospheric humidity is around 98 percent. UTEC, the country's major university of engineering and technology, took this peculiar problem and—with help from ad agency Mayo Draftfcb—devised a unique solution: a billboard that draws moisture out of that humid air and turns it into potable drinking water. Check out the case-study video below to see how it works. The billboard wasn't just a nice gesture, either.