When we talk about the Seven Wonders of the Ancient World, we’re generally talking about things that we can safely assume actually existed. This becomes a little trickier when you’re talking about the Hanging Gardens of Babylon, which is a lost wonder in more than one sense: not only can we find no remaining pieces of the gardens now, but we have only outlandish and contradictory documentary evidence that they ever existed in the first place. This doesn’t mean that they didn’t; it just means that they may as well not have, as far as we’re concerned.
The first writer to document the existence of the Hanging Gardens was the third-century BCE physician Berossus, who wrote the Babylonica as a way of describing Mesopotamian history and culture to his Greek overlords. Only fragments survive. One, quoted by the later Roman historian Josephus, tells the most well-known version of the Hanging Gardens story but provides minimal description of the Gardens themselves:
“When [Nebuchadnezzar II] had thus admirably fortified the city, and had magnificently adorned the gates, he added also a new palace to those in which his forefathers had dwelt, adjoining them, but exceeding them in height and splendor. Any attempt to describe it would be tedious: yet notwithstanding its prodigious size and magnificence it was finished within fifteen days. In this palace he erected very high walks, supported by stone pillars; and by planting what was called a pensile paradise, and replenishing it with all sorts of trees, he rendered the prospect an exact resemblance of a mountainous country. This he did to gratify his queen, because she had been brought up in Media, and was fond of a mountainous situation.”
Except for the bit about the Babylonian people building a massive palace in two weeks (and remember: Berossus was writing 300 years after Nebuchadnezzar’s reign), this sounds plausible enough—he’s basically describing a rooftop garden, ordinary now but extremely rare in the ancient world (though it’s likely that the Babylonians knew how to build screwpumps, which would have made these kinds of gardens possible). There’s no reason any evidence of it should still exist.
But later writers describe something more durable, something we would be less likely to overlook. Consider for example this description by Strabo of Amaseia (ca. 64 BCE to 25 CE), who writes:
“The garden is quadrangular in shape, and each side is four plethra (123.2m/404’) in length. It consists of arched vaults, which are situated, one after another, on checkered, cube-like foundations. The checkered foundations, which are hollowed out, are covered so deep with earth that they admit of the largest of trees, having been constructed of baked brick and asphalt—the foundations themselves and the vaults and the arches. The ascent to the uppermost terrace-roofs is made by a stairway; and alongside these stairs there were screws, through which the water was continually conducted up into the garden from the Euphrates by those appointed for this purpose. For the river, a stadium in width, flows through the middle of the city; and the garden is on the bank of the river.”
Note the detail about the screws. The screwpumps, known in Greece as Archimedes’ screws, were probably known to the Babylonians of Nebuchadnezzar’s day—so this is entirely plausible. But how on Earth did archaeologists manage to miss a 160,000-square-foot structure in Babylon?
Oxford University’s Stephanie Dalley, who has spent her entire professional life studying the Ancient Near East, wrestled with this question and has come to a surprising answer: the Hanging Gardens of Babylon can’t be found in Babylon because they never were in Babylon to begin with. They were in Nineveh, the Assyrian capitol referred to colloquially as the “new Babylon,” and classical historians who suggested otherwise were a bit confused as to its location. (This is quite plausible, actually; historians of the era were notorious for using secondary sources, and it’s unlikely that many of them ever personally visited the region.) This would also explain why we can’t find any evidence of their existence; Nineveh was functionally destroyed in 612 BCE, and we have only a sketchy understanding of what the city looked like in its prime.
As for Berossus, who actually did live in Babylon? Perhaps his more modest Hanging Gardens existed, too—and perhaps the stories of Nebuchadnezzar’s smaller garden in Babylon were conflated with stories of a much larger garden in “new Babylon,” leading to the elusive ancient wonder so many classical historians dreamed about. It’s hard to say, and it will probably remain so.