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. 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..
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.
Fig. 16 Typical cross-section of a valley with cuniculus.
Fig. 17 Direction of cuniculus with respect to the axis of the valley.
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. 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.
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.