One of the first recorded observations about the city of Babylon was made by Herodotus when he visited in the middle of the fifth century BC and the city was still largely as it had been constructed by King Nebuchadnezzar. Herodotus (Appendix A) described the city in grand terms and appears to have either overstated the dimensions of the city or taken the statements of the residents as truth. He claimed that the circumference of the city wall was fifty-six miles and the walls were three hundred feet tall. Archeological evidence has placed this more accurately at ten or eleven miles and only fifty feet tall. Some have thought that perhaps he misunderstood the townspeople and they originally said fourteen miles around, not fourteen miles per side. It is also thought that perhaps Herodotus was including the suburbs of Babylon, in which case his circumference would be more accurate. The map in Figure 2 (Macqueen, 1965, pp. 154) shows the excavated remains of the city and an approximate city layout. The river Euphrates runs through the city and many of the moats around the city were constructed during the reign of Nebuchadnezzar.
Regardless of whether the city wall was fifty-six miles around or only fourteen, it was still impressive. There were actually two city walls and each wall had two distinct parts. The first layer of the outer wall was approximately fifty feet tall and twenty-five feet thick constructed of baked brick. The second layer of the outside wall was again fifty feet tall but only twenty-three feet thick and made of unbaked clay. For mortar, hot bitumen was used which is a petroleum byproduct and quite strong upon hardening. The source for all of this clay was derived from the three hundred foot wide moat which encircled the outer wall and diverted part of the Euphrates around the city as a protective barrier. The two layers of the outer wall were approximately thirty-seven feet apart. This area was filled with rubble and earth so the two layers were joined for a total wall thickness of over eighty feet. On top of this massive wall and actually on top of each of the two walls, watch towers were stationed every one hundred twenty-five feet and each of these towers were approximately twenty-five feet tall. Altogether, this outer wall would have been almost impregnable to an enemy. In front of the outside wall, there was a ten foot thick wall of baked brick below the surface protecting the outer wall from the moat. (Macqueen pp. 159) The massive width of this great wall had many uses. During times of attack, it acted as a highway for the troops to rapidly move from one sector of the city to the other. Since the wall was so wide, chariots being pulled by four horses abreast could easily ride, turn around, and pass each other and allowed for rapid transport.
The massive volume of bricks required for such a construction will now be estimated. Assuming each brick is eighteen inches long, twelve inches wide, and twelve inches tall, and assuming the wall went below the surface twenty feet, it would require approximately 130 million bricks! The rubble and earth required to fill the gap between the two layers was approximately 3.6 million cubic feet! This was a massive undertaking indeed. (Appendix D)
There was also an inner defensive wall of unbaked clay bricks and again using the double layer construction technique. The outer layer of this wall was about twenty-one feet thick with a twenty-three foot gap and then the second layer was twelve feet thick. This time, the space between the two walls was left unfilled. The length of this wall was approximately five and a quarter miles long. Roughly sixty-five feet outside of this wall was another moat estimated at two hundred fifty feet wide. Assuming the same size bricks were used for this inner wall, built to the same height, and with a similar supportive wall for the moat as the outer defense, an estimate on the number of bricks used is approximately 46.4 million. Altogether, the two defensive walls used over 180 million bricks! There is indeed archaeological evidence that such a large amount of bricks were used. Since the destruction of Babylon in about 324 BC, the local villagers and even governments have been pillaging the ruins for bricks in order to build houses, roads, and even dams over the last two thousand years. (Champdor, 1958, pp. 156) That there are still ruins left is a testament to the huge number of bricks with which the city walls were constructed.