On the Orientation of Roman Towns in Italy

Abstract

As is well known, several Roman sources report on the existence of a town foundation ritual, inherited from the Etruscans, which allegedly included astronomical references. However, the possible existence of astronomical orientations in the layout of Roman towns has never been tackled in a systematic way. As a first step in this direction, the orientation of virtually all Roman towns in Italy (38 cities) is studied here. Non-random orientation patterns emerge from these data, aiming at further research in this field. The planning of a Roman townDuring the republican period and the first imperial period (roughly from the V century b.C. to the I century a.D.) the Romans founded many towns, or colonies. The foundation of a town was an efficient method in order to establish permanent control on a newly conquered land, and a consistent amount of people (up to 5000 families) was assigned to the new towns in accordance with a legal act called deductio. The urban plan of the settlements was always the same: the layouts of the newly founded towns were indeed planned in accordance with the so called castrum (i.e. military camp) structure.1 A colony could also be deducted "on" a pre-existing, non-Roman town, either conquered or allied; also in this case however, the layout was usually re-designed in accordance with the Roman standards (see e.g. Sommella 1988). The city boundaries of a castrum town formed a rectangle, usually not very stretched in one direction or the other, so that we can refer generally to this kind of town planning as to a squared one. The rectangle was delimited by the walls and the internal streets were organized in a orthogonal grid forming the inhabited quarters (insulae). As is well known, orthogonal town planning -which has been a common feature of many cultures, for instance the Hindu one -was theorized in the classical world by the Greek architect Hippodamus of Miletus around the half of the V century, and applied strictly in all Greek colonies (Castagnoli 1971). Beyond any doubts it was applied by the Etruscans as well, as it is shown by the excavations at Misa, the unique known Etruscan town which was conquered by the Celts and abandoned before the Roman expansion (Mansuelli 1965). Some authors believe that the Etruscans simply copied the orthogonal plan from the Greeks, but in any case it is reasonable to think that the Romans inherited the orthogonal layout from the Etruscans, rather than from the Greeks. In addition to the orthogonal layout however, the inspiring principle of the Roman castrum was based on the existence of two main orthogonal roads, called cardus and decumanus. Thus, in Roman towns, the orthogonal layout was actually quadripartite: at the end of the four main roads, four main gates were located, while the centres of the social and religious life (the Forum and the main temple or Capitolium, respectively) were preferably placed at (or near) the intersection of the main roads (see e.g. Rykwert 1999). To fix ideas about a Roman castrum town, we can look at Fig. 1, where, as an ...

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