Researchers credit the Hanging Gardens of Babylon as the first examples of green roofs. Although there is no proof of its exact location and very little literature on the structure, the most accepted theory is that King Nebuchadnezzar II built a series of elevated, ascending terraces with varied species as a gift to his wife, who missed the forests and mountains of Persia, their local land. According to Wolf Schneider  the gardens were supported by brick vaults, and under them, there were shaded halls cooled by artificial irrigation of the gardens, with a much milder temperature than the outside, in the plains of Mesopotamia (present-day Iraq). Since then, examples of green roofs have appeared all over the world, from Rome to Scandinavia, in the most diverse climates and types.
Nevertheless, inserting plants on roofs is still viewed with suspicion by many, as they are thought to be costly and difficult to maintain. Others, however, argue that the high implementation costs are quickly offset with savings in air conditioning and especially that occupying the building's fifth façade with vegetation is, above all, a rational solution. In any case, the question remains as to how green roofs can really help with climate change.