Six of the Seven Wonders of the Ancient World left a physical footprint. The Hanging Gardens of Babylon left nothing, and generations of scholars concluded they were fiction. This episode treats the missing wonder as an archaeological cold case, starting with the traditional story that Nebuchadnezzar II built terraced gardens for his homesick Median wife, then asking why his exhaustive building records, the historian Herodotus, and modern excavations in Babylon are all silent.

The trail leads to Oxford scholar Stephanie Dalley's theory that the gardens were real but stood 300 miles north in Nineveh, built by the Assyrian king Sennacherib. We look at his own inscriptions, his 50-mile network of canals and aqueducts with automatic sluice gates, his claim to have cast 30-ton bronze water screws, and a palace relief that appears to show the gar ...