The Hanging Gardens of Babylon are the only one of the Seven Wonders of the Ancient World whose actual location has never been definitively established by archaeology. According to ancient Greek accounts, they were built by King Nebuchadnezzar II for his wife, Amytis of Media, who missed the green hills of her homeland. The gardens were described as a series of tiered terraces supported by stone columns, filled with a vast array of trees, shrubs, and vines. To keep the vegetation lush in the arid climate, an advanced irrigation system—possibly involving a chain pump or an Archimedes' screw—would have been required to lift water from the Euphrates River. Some modern scholars suggest the gardens may actually have been located in Nineveh and built by the Assyrian King Sennacherib, while others believe they were a poetic metaphor for the grandeur of Babylonian architecture.