Ravelli: Etruscan cuniculi (1984)

4. The cross-section of a typical cuniculus visible on the working face of a modern quarry for the extraction of tufo blocks is shown in Figures 1, 14. This cuniculus runs roughly parallel to the contour line of the hill with a slight downward slope. The permeability of the volcanic tufo in which this cuniculus has been excavated decreases from top to bottom. Thus the water which filters through the vault of the cuniculus can flow without seeping through the floor. In this particular cuniculus a trough (doccia) has been excavated along the left wall to collect the water. This made it possible for a person to enter the cuniculus without dirtying the water collected (Figure 15).

Fig. 14 Detail of the cuniculus photographed in Figure 1. The foot of one of the authors (P. Howarth) rests on one of the tufo blocks cut from the quarry.

Fig. 15 Detail of the cuniculus photographed in Figures 1 and 14. A trough has been cut on the left-hand wall for the collection of filtered water..

Most of the Etruscan cuniculi in Latium have the same position with respect to the contours of the ground surface as the one mentioned above. These characteristics are not, however, always immediately obvious on account of changes in the earth's surface that have come about over the years. In areas that have not been urbanized, however, the landscape has changed less than one might suppose. Thus a careful examination makes it possible to see, objectively, how the location of the cuniculus was related to its function: i.e. how the collection of water that has filtered down through the upper layers of soil and flowed along the inclined plane between the deep-lying impermeable layers and the superjacent permeable ones (Figures 16, 17).

Fig. 16 Typical cross-section of a valley with cuniculus.

Fig. 17 Direction of cuniculus with respect to the axis of the valley.

When water seeped through the floor of a cuniculus, especially the late ones the lower part of the tunnel was lined with an impermeable plaster (Figure 8 G). This practice would have been counterproductive had the cuniculus been excavated for drainage purposes.
Thus it is hard to see how, in the past (and also recently), it could have been suggested that the function of the whole network of cuniculi was reclamation of the entire territory. Many factors exclude that possibility: the position of cuniculi in the hills, the fact that the density of cuniculi was insufficient to guarantee reclamation; the random location of the cuniculi and simple economic/hydraulic considerations.
Although the function attributed to cuniculi by the authors of this paper had already been suggested in the past by the illustrious scholars Fraccaro and, subsequently, Secchi and Celli, they did not look into the question of the characteristic position of cuniculi with respect to the direction of the flow of infiltrated water nor did they examine the reason for which cuniculi are dry today. This is a fundamental factor in understanding the technological prowess and the advanced reasoning (for that period) that such an undertaking implied. The fact that cuniculi were excavated for this purpose testifies to the high level of civilization and sanitation already achieved by those populations which, only a few centuries later, generated one of the greatest and long-lived civilizations of antiquity in the west.
Another example of a cuniculus for collecting drinking water is the one discovered in 1921 during the excavation of the Etruscan sanctuary, composed of a temple and adjacent pool used during the Etruscans' religious rites, at Veio (Figures 18, 19). Temple, pool and cuniculus all date from the mid 6^th century B.C. The cuniculus excavated by the Etruscans for the collection of drinking water which had filtered through the superjacent hill. is located on the north side of the sacred area at the side of the main road into Veio. This cuniculus, like the one visible from the Tiberina road, has a little trough (Figure 20) excavated in one of its walls about 70 cm above the floor. This trough collected also the water coming from a secondary branch of the cuniculus which was then transported by aqueduct to a cistern. The water which collected on the floor of the cuniculus ran off into a little man-made trough still visible today, which led to the pool.
Neither this cuniculus nor the one near the Via Tiberina carry water today.
An interesting and rare feature of the cuniculus at the sanctuary in Veio is that we can see where the water went and how it was utilized.

Fig. 18 Cuniculus located near the sanctuary at Veio. Note the road into Veio, the cuniculus and trough for carrying the water to the pool.

Fig. 19 Plan and cross-section of the cuniculus shown in Figure 18. (C - cuniculus, A - aqueduct, D - trough, E - pool, F - temple, B - road).

Fig. 20 Interior of the main cuniculus shown in Figure 19.

Another very interesting cuniculus is the one located at the foot of the Capitoline hill in the heart of Rome. It too penetrates into the hill to intercept water which has filtered down through the hill (Figure 21). The floor and lower part of the walls of the cuniculus were lined to avoid water loss. Obviously this feature is hardly compatible with the drainage theory. The cuniculus is easy to see as part of the hill has been cut off to make way for a U curve in the modern street via Monte Tarpeo (Figure 22).

Fig. 21 Cuniculus located in the Capitoline hill. It has been cut into two sections by the modern street. Note that the cuniculus in the foreground (of which only the lower part remains) has been lined (opus signinum).

Fig. 22 Plan of the cuniculus shown in Figure 21.

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