The ancient city of Babylon, under King Nebuchadnezzar II, must have been a wonder to the traveller's eyes. "In addition to its size," wrote Herodotus, a historian in 450 BC, "Babylon surpasses in splendour any city in the known world." Herodotus claimed the outer walls were 56 miles in length, 80 feet thick and 320 feet high. Wide enough, he said, to allow a four-horse chariot to turn. The inner walls were "not so thick as the first, but hardly less strong." 
Inside the walls were fortresses and temples containing immense statues of solid gold. Rising above the city was the famous Tower of Babel, a temple to the god Marduk, that seemed to reach to the heavens. While archaeological examination has disputed some of Herodotus's claims (the outer walls seem to be only 10 miles long and not nearly as high) his narrative does give us a sense of how awesome the features of the city appeared to those that visited it. Interestingly enough, though, one of the city's most spectacular sites is not even mentioned by Herodotus: The Hanging Gardens of Babylon, one of the Seven Wonders of the Ancient World.


The hanging gardens

Accounts indicate that the garden was built by King Nebuchadnezzar, who ruled the city for 43 years starting in 605 BC (There is a less-reliable, alternative story that the gardens were built by the Assyrian Queen Semiramis during her five year reign starting in 810 BC). This was the height of the city's power and influence and King Nebuchadnezzar constructed an astonishing array of temples, streets, palaces and walls.
According to accounts, the gardens were built to cheer up Nebuchadnezzar's homesick wife, Amyitis. Amyitis, daughter of the king of the Medes, was married to Nebuchadnezzar to create an alliance between the nations. The land she came from, though, was green, rugged and mountainous, and she found the flat, sun-baked terrain of Mesopotamia depressing. The king decided to recreate her homeland by building an artificial mountain with rooftop gardens.
The Hanging Gardens probably did not really "hang" in the sense of being suspended from cables or ropes. The name comes from an inexact translation of the Greek word kremastos or the Latin word pensilis, which mean not just "hanging", but "overhanging" as in the case of a terrace or balcony.
The Greek geographer Strabo, who described the gardens in first century BC, wrote, "It consists of vaulted terraces raised one above another, and resting upon cube-shaped pillars. These are hollow and filled with earth to allow trees of the largest size to be planted. The pillars, the vaults, and terraces are constructed of baked brick and asphalt."
Diodorus Siculus, a Greek historian, stated that the platforms on which the garden stood consisted of huge slabs of stone (otherwise unheard of in Babel), covered with layers of reed, asphalt and tiles. Over this was put "a covering with sheets of lead, that the wet which drenched through the earth might not rot the foundation. Upon all these was laid earth of a convenient depth, sufficient for the growth of the greatest trees. When the soil was laid even and smooth, it was planted with all sorts of trees, which both for greatness and beauty might delight the spectators."
How big were the gardens? Diodorus tells us it was about 400 feet wide by 400 feet long and more than 80 feet high. Other accounts indicate the height was equal to the outer city walls. Walls that Herodotus said were 320 feet high. In any case the gardens were an amazing sight: A green, leafy, artificial mountain rising off the plain. But did it actually exist? After all, Herodotus never mentions it.
This was one of the questions that occurred to German archaeologist Robert Koldewey in 1899. For centuries before that the ancient city of Babel was nothing but a mound of muddy debris. Though unlike many ancient locations, the city's position was well-known, nothing visible remained of its architecture. Koldewey dug on the Babel site for some fourteen years and unearthed many of its features including the outer walls, inner walls, foundation of the Tower of Babel, Nebuchadnezzar's palaces and the wide processional roadway which passed through the heart of the city.
While excavating the Southern Citadel, Koldewey discovered a basement with fourteen large rooms with stone arch ceilings. Ancient records indicated that only two locations in the city had made use of stone, the north wall of the Northern Citadel, and the Hanging Gardens.
The north wall of the Northern Citadel had already been found and had, indeed, contained stone. This made it seem likely that Koldewey had found the cellar of the gardens. He continued exploring the area and discovered many of the features reported by Diodorus. Finally a room was unearthed with three large, strange holes in the floor. Koldewey concluded this had been the location of the chain pumps that raised the water to the garden's roof.
The foundations that Koldewey discovered measured some 100 by 150 feet. Smaller than the measurements described by ancient historians, but still impressive.
One can only wonder if Queen Amyitis was happy with her fantastic present, or if she continued to pine for the green mountains of her homeland.