Irrigation and water supply systems were part of this. Aqueducts, of course, had existed in Sicily since Roman times, if not earlier. Parts of a Roman aqueduct are still visible in the Sicilian town of Termini Imerese, for example, and the city of Rome was itself supplied water by a sophisticated series of aqueducts. The Arabs, however, expanded irrigation to the extent that crops requiring more water than almonds, olives and hard wheat could now be grown on a large scale. Cultivation of sugar cane, lemons, oranges and mulberries became popular during the Arab period. But it was in the urban setting that the greatest feats of construction were to be seen (actually "seen" by a few, as these were often underground). Punic Palermo could rely largely on its rivers for fresh water; this was no longer the case in the greatly expanded city of the Arabs..

Under the Arabs, Bal'harm (Palermo) became the largest of Sicilian cities. Indeed, it was the Arabs who made it the island's capital, which under the Byzantines was Syracuse on the Ionian coast. Estimates of the expansive city's Saracen-era population vary widely, but two hundred thousand is a reasonable figure. Water supply was obviously an important problem in medieval Palermo, one of the largest European cities of the tenth century.

The solution was a series of channels that brought water from springs in the Monreale area into the city. A few of these springs --one of which fed the Kemonia River-- still run under the old city today. Most of the channels extended from the Baida and Altofonte districts, still known for their mineral springs, across vast rural areas to the city. Under the Normans, these became vast royal parks and hunting grounds, and the water supply was still protected. A few of the surface channels can still be seen in this area.

In the city, the channels were constructed far underground. This was practical to avoid the potential contamination of above-ground networks, and for convenience, but it was also necessary for the channels to become gradually deeper to permit gravity-based water flow --the same principle employed in the Romans' aqueducts. The Arabs used the term kanat (qanat) to describe these channels, and several still exist today in the area between the royal palace and the Quattro Canti. Thee network was greatly expanded in the time of Roger II, and Abdullah al Idrisi mentioned it in his descriptions of Palermo. In fact, fresh water still flows through some of the channels. Several were still in use well into the sixteenth century, long after the Arabs had melded into the general Sicilian population. The Arabs' descendants may have forgotten about their medieval ancestors, and even modified many Norman-Arab buildings beyond recognition, but the kanats survived. It has even been suggested that the Beati Paoli might have used some of the subterranean passages to mysteriously vanish into the night.

What is remarkable is how little the fundamental principles of this kind of engineering have changed over the centuries. The materials are different, but while flow mechanics have remained constant, gravity-fed systems are no longer the only approach to designing water delivery systems.

Unfortunately, efforts to open the kanats to guided tours have not proven entirely successful, but the existence of such passages reminds us that many of Bal'harm's secrets are yet to be revealed.

About the Author: Architect Carlo Trabia has written for various magazines and professional journals, as well as this online magazine.