When Nature Calls is a conceptual urination system (just go with it) that aims to make the process of using a public urinal greener and more pleasant. The system uses its urine intake to water an on-board grove of plants.

All you have to do is take a leak and When Nature Calls will run the urine through a three step filtration system involving limestone, green sand and charcoal. The resulting water is then used to feed the plants. The system's designer, Eddie Gandelman, says the product design of four urinals around a cylindrical "pod" offers more space and privacy for users.

Well, if it's good enough for Bear Grylls, certainly it's good enough for foliage.