An attentive observer of the details of the landscape will sometimes also note, at the base of hills, bushes at intervals along the contour lines (Figure 3). These bushes, green all year round, are particularly noticeable in the summer when the rest of the vegetation (in the Mediterranean region) is sparse and withered. When closely observed it is easy to see that these bushes are growing around the lips of vertical shafts which connect the vault ceiling of the tunnel with the ground surface.
Fig. 1 Cuniculus near the Via Tiberina. The marks on the quarry wall were made by the saw as it cut the tufo blocks.
Fig. 2 Cuniculus near the Via Appia Pignatelli.
Water still flows (0.5-1 l/s) in a few of these tunnels. More often, however, they are dry. In many cases they are either partially or totally plugged by transported soil and calcareous deposits (Figures 1, 2, 4, 5).
Fig. 3 The countryside on the outskirts of Rome. Note the bushes growing around the lips of the vertical shafts which serve to ventilate the cuniculus. The shaft in the foreground of the photograph has caved in.
These are the tunnels, called cuniculi (from the Latin cuniculus(i)), excavated by the Etruscans in the geological formations created by the eruptions of the now extinct volcanoes which extend in a line roughly parallel to the Tyrrhenian Sea just north and south of Rome (Figure 6).
Fig. 4 Pair of cuniculi near Via Sicilia in Rome which pass under the Aurelian wall of the city. The cuniculus on the left-hand side of the photograph is partially plugged by calcareous deposits; the one on the right by fine soil.
Fig. 5 Detail of the cuniculus on the left-hand side of the photograph in Figure 4.
The many types of excavations made in Roman and pre-Roman times in the subsoil of Latium may be classified according to the purposes they served : (1) tunnels for collecting water which has percolated down through the overlying strata and filtered through the tunnel walls; (2) tunnels for reclamation purposes (drainage); (3) tunnels for collecting perennial spring water; (4) diversion works; (5) aqueducts; (6) sewers; (7) outlets of lakes; (8) passages (used also for military purposes); (9) places of worship; (10) animal shelters; (11) quarries; (12) Early Christian cemeteries (catacombs).
Fig. 6 Orography of Latium showing the now extinct volcanoes. The black dot marks the city of Rome.
The cuniculi located in this area are basically rectangular tunnels with a barrel or ogival vault (Figures 8 A, B). They are from 1. 7 to 2. 0 m high and 60 to 70 cm wide. Communication between the cuniculus and the ground surface is provided by a series of narrow shafts spaced at a distance of 40 to 60 m from one another along the cuniculus. In some cuniculi a continuous shelf, excavated along the length of one of its walls, served as resting place for the excavator's tools and a lantern to light up the working face (Figure 8C). The walls of cuniculi were not generally faced. Only rarely does one find the lower part of the walls covered with a mixture of lime and crushed terra-cotta shards known in Roman times as opus signinum (Figure 8E). The marks left by the excavator's pick as he worked at the rock, swinging his arm in a downward arcuate movement, are often still visible on the walls of cuniculi (Figure 9). The cuniculus was generally driven from the lower level to the higher one. Sometimes, when driven simultaneously from the two different directions, it was only by a few centimetres that the two segments of the approaching cuniculus were out of an alignment at the point of juncture. This is proof of the precision of the workmanship. On account of the orography, cuniculi very rarely exceeded several hundred metres in length. Sometimes several cuniculi running in different directions can be found, at different depths on the same vertical. Although complex systems of intercommunicating cuniculi have been found, generally, each cuniculus is clearly autonomous and separate from the others.
Fig. 7 The shaded area indicates the volcanic formations of Latium. In the 8th century B.C., the Etruscan culture was established north of Rome. It had a strong influence on the Latins who had settled south of Rome. The cuniculi found by the authors are indicated by the black dots.
The vertical entrance shafts, providing ventilation and facilitating the extraction of debris, are rectangular with a section area of about 1 to 2 square metres. Notches dug into the two main walls of the shaft allowed the excavator to get a good foothold as he descended the shaft (Figures 10, 11).
Fig. 8 Cross-sections of different types of cuniculi.
Fig. 9 Wall of a cuniculus showing the excavator's pick marks.
Fig. 10 Vertical shaft of one of the cuniculi shown in Figure 4. This photograph, taken in 1953, shows one of the authors during an exploration of the cuniculus.
Fig. 11 Cut-away view of the same shaft as in Figure 10. Note the point where the shaft meets the ceiling of the cuniculus. A thick calcareous deposit is visible on the wall of the shaft.
Fig. 12 Fragments found in the debris extracted from the shaft. On the bottom of a terra-cotta cup (3rd century B.C.) the name of the proprietor has been scratched in black paint: BITUS.
Cuniculi spread out in Latium for hundreds and possibly thousands of kilometres. It is, in fact, hard to determine the exact extent of cuniculi partly because they have not been systematically explored and any discoveries are purely casual; and partly because most of the shafts have filled in and are, therefore, invisible from the surface.
The authors of this paper believe that the cuniculi were excavated almost exclusively for the purpose of obtaining pure water that had been made suitable for drinking by the filtering action of the earth on rainwater. Any other hydraulic functions were, in the authors' opinion, absolutely secondary. Cuniculi were probably excavated between 800 B.C. and 400/300 B.C. by the Etruscans in Southern Etruria and the Latins, influenced by the Etruscans, in Latium Vetus, only in the geological deposits of volcanic origin.
Many other functions may be attributed to the numerous varieties of excavations made in antiquity in Latium. But these are always structurally different from cuniculi and should not, therefore, be confused with them.
1 These formations were created by the settling of material projected from volcanoes in eruption. The degree of consolidation and permeability varies : pozzolana is friable and permeable whereas tufo is stonelike and either semi-permeable or impermeable.