Sure, the Hanging Gardens aren't mentioned anywhere, but as World History notes, Herodotus left the Great Sphinx out of his description of the Giza complex entirely, and we definitely know the Sphinx is, in fact, a thing that's there. Since historians have an example of ancient writers not acknowledging monuments that are definitely there, that can add another check in the "maybe" category.
It's also worth considering that the Hanging Gardens of Babylon were sometimes referred to by a different name: the Hanging Gardens of Semiramis. That clears up absolutely nothing, because Semiramis comes with her own set of questions. She was an Assyrian ruler from the 9th century BC — a few centuries before Nebuchadnezzar. Her original name, says National Geographic, was Sammu-ramat before it was Hellenized to Semiramis, and no one can really decide what she was.
Sammu-ramat ruled for just five years, and records have her as a fearless military leader, the builder of Babylon, a tragic figure at the center of an ancient love story, and some credit her with a semi-divine heritage. It was the Greek writer Strabo who credited her as being the creator of the garden, but according to Oxford Reference, Strabo lived between 63 BC and 23 AD. That was nine centuries after Sammu-ramat, and it's unclear just where this idea came from — there's no historical records of such a connection.
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