The geological heterogeneity of Naples and of its adjacent areas is probably without equal in the world. Surrounded by volcanoes, volcanic lakes, volcanic islands, fault lines and karst phenomena,its territory was shaped and modelled in a unique way difficult to find elsewhere. The energy unleashed by the activity of Vesuvius, and Phlegraean Fields, gave rise to lush and luxuriant plant life that feeds on the earth’s natural fertilizers – a large variety of mineral springs disseminated throughout the Bay of Naples, the underwater remains of volcanic cones, and the socalled “secche” – shoals once teeming with coral. Clearly, human life was strongly conditioned by these geomorphological situations, by such earth movements as bradyseism. And what we see now, starting from the genesis and features of Neapolitan soil, is the result of human activities and manmade alterations, gradually developing over the course of the last three thousand years… Since antiquity, Neapolitan subsoil has seen the opening of myriad cisterns, quarries, passageways, catacombs, and more, becoming genuine road axes designed and built to traverse parts of the territory. Naples’s underground settings thus present so vast and diversified a horizon that it is assessed as reaching a volume equalling about one million square metres of area; but according to some estimates, there is far more to be discovered: beneath our feet there might be two million more square metres yet to be surveyed; therefore, approximately 60% of Neapolitans live and work above a cavity. Without going into detail on the countless quarries, cavities, cisterns, and catacombs – at least those verified in terms of location and age of construction – discussion here will regard only those road tunnels built in the Augustan Age, some of which were likely to have been part of a unique military/transport project designed and conceived by Marcus Vipsanius Agrippa; their chief maker was the Augustan Age Roman architect and engineer Lucius Cocceius Auctus. But first, the ancient methods of tunnelling, probably the same used in the Roman Age and handed down until just a few short decades ago – that is, until the rise of modern machinery – merit discussion. One cannot stress enough the local workers’ considerable expertise – well-known since ancient times. It was no accident that to Strabo, these workers appeared to be descendents of the Cimmerians, who were said to have inhabited the area centuries earlier, dwelling in underground tunnels. This expertise was handed down over the years, making the quarrymen and excavators famous in our own time. In the following description, some terminology used in the excavators’ vernacular will also be discussed.