Studying the geological origins of an urban area is about understanding the reasons for its form, and most of all, its primal underpinnings. Geology is much more fundamental than other instruments to explain the evolution of large historical cities such as Rome and its spatial and temporal scale. The two factors here are the nature and hazards of the terrain and the topography generated by the millenarian interaction of geological activity. Geology is a common ground for the whole urban agglomeration, reducing the superficial heterogeneity of the city to a territorial homogeneity. Rome’s urban landscape is a wonderful but unresolved superposition of countryside, Agro Romano , and a constructed city. One of the main conditions for the spread of an urban area is the balance between the potential and the risks inherent in a site, both dependent on the level of technology reached by society. In the case of Rome, the hilly nature of its landscape has represented, since its origin, both a potential and a problem. At the beginning of third millennium BC several villages settled along the left bank of the Tevere (Tiber River). The sites were strategically located in a volcanic area cut through by the Tiber fluvial network, leaving isolated tuffaceous cliffs that dominated the alluvial plain. Such a setting was favourable because of the
abundance of springs and building stones, very useful for the technological development of building and infrastructures. The good microclimate of these higher elevations was a strong protection from malaria, endemic to the plains of the river and the Tyrrhenian coast. Rome was one of these proto-historic villages, settled on the Campidoglio (Capitol Hill), the closer of the seven hills to the Isola Tiberina (Tiber’s Island). This location permitted both easy defence and permanent control of the mercantile trade at one of the rare points where it was possible to cross the flow of the Tiber. Indeed, the proximity to the other six hills guaranteed a certain degree of continuity, despite the difficult topography. The hilly landscape of the Campagna Romana originated in a Quaternary tectonic, erosive and volcanic phenomena that started one million years ago when the region was lifted out of the sea. The sandy formations of Monte Vaticano were suddenly eroded by a fluvial network – at the time, the Paleotiber (the ancient Tiber River) started in the Appennines and had its delta in Ponte Galeria. Between 600,000 and 700,000 years ago the Monte Mario ridge emerged in the northwest of the area. Together with the Pomezia formation, the Monte Mario ridge forced the Paleotiber eastward, moving its delta nearer the Anzio village.
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opposite: Rupe Tarpea, Roma right: Climbing Via di Monte Tarpeo
giulia piana
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