Here is a fairly classic statement of the case for scepticism(complete with nice picture). There are two components:
An intensive web search has failed to produce a single citation regarding the Hanging Gardens in ancient poetry. The search did produce the 19th-century poem at the bottom of this page, which fits the apparent mindset of the late 19th and early 20th century. But a library foray produced The Seven Wonders of the Ancient World, Peter Clayton & Martin Price (eds), Dorset Press (New York) 1988, 38-58, which quotes Antipator of Sidon, a Greek poet, 2nd Century BC. A web search for this poet indeed produced the poem in a malfunctioning website that had not otherwise made it into the search engines. Here is the poem:
I have gazed on the walls of impregnable Babylon,
along which chariots may race,
and on the Zeus by the banks of Alphaeus.
I have seen the Hanging Gardens and the Colossos of Helios,
the great man-made mountains of the lofty pyramids,
and the gigantic tomb of Maussollos.
But when I saw the sacred house of Artemis that towers to the clouds, the others were placed in the shade, for the sun himself has never looked upon its equal outside Olympus.
Clearly, this poem alone could never support the idea that the Hanging Gardens only existed in the minds of "Greek Poets". Fortunately, the same book by Clayton and Price includes a chapter by Irving Finkel, who provides a longer extract of Quintus Curtius than you can find on the web. In Finkel's version, Quintus Curtius comments that the gardens are "a trite theme with the Greek poets".
Quintus Curtius seems to be doing something rather careful here. We have seen that there is almost no reference to the gardens by Ancient Greek poets - Antipator of Sidon, quoted above, merely mentions them in passing, and no one else seems to mention them at all. Of course, it is possible that we have lost all the relevant poems in the 2000+ years since they were written. It is possible. But what if there never were any Greek poems on the gardens? All you would have left then is a "trite theme with the Greeks" - which is what the marginal note in Diodorus said. We have seen that Ctesias, Clitarchus, Diodorus and Strabo all discussed the gardens in detail; as did Philo of Byzantium (if it was him, and if he was Greek). So the theme was at least well-known among Greek writers. It is as if Quintus Curtius was trying to remind us of those Greek writers while also distancing himself from them. Why would he do that?
It seems that his History of Alexander the Great of Macedonia (which contains the description of the Hanging Gardens) was really a grim analysis of the insane Emperor Caligula in disguise. So we know that Quintus Curtius can hide his agenda quite cleverly. It also seems that Rome was in process of adding "Assyria", which included Babylonia, to its empire when Quintus Curtius wrote. If he could disguise the unpalatable truth about Caligula in a "history of Alexander", surely he could also disguise the unpalatable truth about the garden builder in a "trite theme", complete with a "mistake" about who was responsible for that theme.
The idea that Alexander's troops might have conflated the walls and ziggurat of Babel to produce the gardens needs dating. Stickney's poem may date popular awareness of the idea. Kind of gels well with the advent of phenomenology and its tenets too. Post entropy.Poem by Trumbull Stickney
Jessie B. Rittenhouse, ed. (1869–1948). The Little Book of Modern Verse. 1917. 42. Be Still. The Hanging Gardens Were a Dream By Trumbull Stickney (1874-1904) BE still. The Hanging Gardens were a dream That over Persian roses flew to kiss The curlèd lashes of Semiramis. Troy never was, nor green Skamander stream. Provence and Troubadour are merest lies, 5 The glorious hair of Venice was a beam Made within Titian's eye. The sunsets seem, The world is very old and nothing is. Be still. Thou foolish thing, thou canst not wake, Nor thy tears wedge thy soldered lids apart, 10 But patter in the darkness of thy heart. Thy brain is plagued. Thou art a frighted owl Blind with the light of life thou'ldst not forsake, And Error loves and nourishes thy soul.
Introduction Getting Started Listing the Sources The Eye Witnesses The Descriptions The Relief Herodotus Ctesias Clitarchus Berossus Philo Diodorus Strabo Quintus Curtius Problem 1: The Garden Creators Problem 2: A Matter of Truth A Real Hanging Garden History of Disbelief Visual Reconstructions Conclusions