The hanging gardens of Babylon

The hanging gardens of Babylon are a quite mysterious wonder. Indeed, no Babylonian text describing them have been found. We don't even know the destruction date of this wonder. Maybe this is just a product of Greeks imagination ?
The gardens were located on east the bank of the river Euphrates, in the city of Babylon (50 km from Bagdad) and may have been built in 600 bc. No Greek historian have seen them, it just consists in stories told by soldats, which is a quite doubtful source of informations.
According to the legend king Nebuchadnezzar II (604-562 BC) would have made build the famous hanging gardens of Babylon for his wife Sémiramis to remind her the vegetation of the moutains from her natal country : Media (actual Iran).
These gardens were composed of several floors, each was a terrace of 120 m² supported by vaults and pillars of brick. An immense staircase, made of marble, connected the terraces, where water was brought from the river Euphrates by a system of hydraulic screws. It was a real botanical garden where was cultivated plants and trees of Mesopotamia and of Media. On the first eight meters height terrace were planted big trees : plane trees, palm trees - date palms, pines and cedars. On the second thirteen meters height terrace were located the cypresses and quantity of fruit trees. And even heigher, on the two last terraces, less vast than the others, we could find the anemones and the tulips, the lilies and the irises… without forgetting the roses, so appreciated from the beautiful Sémiramis.
Why is this a wonder of the ancient world ?
At the time, it was an innovation : for the first time Greeks saw hanging gardens on the roofs. Moreover, the meeting of all this diversity of plants was to be splendid and should have amply satisfy Sémiramis.
Several illustrations :