An extensive rooftop garden

This is a picture of the second rooftop garden we saw on our tour ... The sun was starting to set by the time we got there, and the shadows make it hard to see the actual garden in this picture. So I'll try to describe it for you ... It's an "extensive" garden, which means that the vegetation tends to be smaller and support requirements for the weight are less than the intensive garden. In this instance, the soil is about 6 inches deep, and purchased plants grow with those whose seeds were brought with the wind and soil. Right now the wildflowers/weeds would be in full bloom. This garden also reduces heat, cooling costs, and absorbs toxins from the air.