2. As a variety of opinions have been expressed as to the function of cuniculi, it may be interesting to recall just what historians and experts in various fields have written on the subject.
The word cuniculus was used in Roman times to indicate the subterranean passages that were used to invade cities (cuniculus urbem capere) and to cut off those cities' water supply. In his History of Rome, Tito Livio (59 B.C. - 17 A.D.) mentions Camillo's Roman army's corps of cuniculari used in the conquest of the Etruscan city of Veio in 396 B.C. Perhaps it is no coincidence that there are so many cuniculi in the area surrounding Veio about 15 km north of Rome. Perhaps it was thanks to a network of cuniculi already existing at the time of the invasion that the Romans routed Veio and not as a result of an excavation carried out for military purposes.
Famiano Nardino was the next to write about cuniculi in 1647. He felt that the cuniculi underlying the city wall of ancient Veio were the passages used by Camillo to enter the city.
A. Nibby, perhaps one of the greatest "travellers" in the Roman Campagna, did not agree with Nardini. In his book Viaggio Antiquario ne' Contorni di Roma published in 1819, Nibby stated that, in his opinion, the cuniculi observed by Nardini were merely sewers.
In the following year, G.B. Brocchi, in his famous explanatory memorandum to the geological map of Rome, briefly mentions a cuniculus discovered at the foot of the Aventine hill in Rome but makes no suggestion as to what its function might have been.
About thirty years later A.E. Braun, in a lecture given in 1852 at the Istituto di Corrispondenza Archeologica on the occasion of the anniversary of the founding of Rome, referring to a cuniculus observed at the foot of the Palatine hill in Rome remarks :
"As the volcanic tufo, which forms the depths of the Roman hills, is not only fragile and subject to landslides, but also has a poor resistance to humidity, a special system was needed to protect those inhabited, swampy, unhealthy sites against the effects of gravity and water."
In this study, for the first time, cuniculi were interpreted as being underground drainage tunnels for land reclamation. Braun was the first to attribute the excavation of cuniculi to the Etruscans; previously cuniculi had been held to be the work of the Romans.
In 1857 C.H. Deschemet accurately described the complex network of cuniculi discovered near the church of Santa Sabina on the Aventine hill in Rome not far from the cuniculus mentioned by Brocchi several decades beforehand. These cuniculi had been subsequently adapted and much discussion as to their function led to no definite conclusion. Deschemet's opinion was that they were branches of a Roman aqueduct.
R. Canevari suggested a new hypothesis on the function of cuniculi in his description (1875) of the excavations made on the Quirinal hill in Rome to make way for the foundations of the Ministry of Finances building. Tunnels located on four different levels and branching out into all directions were visible in the layers of tufo and pozzolana forming the subsoil of the construction site. The tunnels at the first and third levels, at depths of 8 and 12 m respectively, each having a cross-section of several square metres, were undoubtedly ancient underground quarries from which pozzolana had been extracted for building purposes. Although the tunnels at the second and fourth levels, at depths of 11 and 22 m respectively were quite definitely smaller, Canevari was only sure that the tunnels at the second level were true cuniculi. He noted that their walls were covered with calcareous deposits and that they were filled with fine clayey material. For this reason he held that the purpose they served was the "scolo delle acque" (water drainage). As no calcareous deposits were found in the cuniculi located at the fourth level, Canevari considered these to have been excavated in a search for new layers of pozzolana. On the basis of Canevari's attempt to date the entire network of tunnels, it would appear that the cuniculi at the fourth level were excavated in the dark ages following the fall of the Roman empire.
Father A. Secchi was the first to interpret the cuniculi as conduits for the collection of drinking water in rural areas. In an interesting paper published in 1876 Intorno ad alcune opere idrauliche antiche rinvenute nella campagna di Roma, Secchi describes cuniculi as a means of collecting water by infiltration through the soil and maintains that this was the method used to provide farmers in the country with a certain quantity of water. Shortly after the modern State of Italy was created in 1870 and Rome became its capital, several studies were published which propounded the old theory that cuniculi were excavated for drainage purposes. At that time technicians were concerned with the problems posed by the swamps surrounding Rome which, since Roman times, had been a source of malaria.
In this framework P. Di Tucci, secretary of the Government Commission for the Reclamation of the Roman Campagna and a dedicated analyst of this problem, published in 1878 a paper entitled Dell'antico e presente stato della Campagna di Roma in rapporto alla salubrità dell'aria e alla fertilità del suolo. Di Tucci basically embraces Braun's old theory, elaborates on it and comes to the conclusion that the network of cuniculi found in the Roman Campagna was a grandiose underground network of drainage conduits created in Roman times. Di Tucci, like many of his contemporaries, was convinced that the unwholesomeness of a territory was the fruit only of an excessive degree of humidity.2
Perhaps the theory that cuniculi were drainage works might not have been so widely accepted had it not been so heartily supported by C. Tommasi Crudeli, a famous medical doctor and expert on the malaria problem which, in those years, was such a burden to the local authorities and the central government itself. In a famous paper published in 1879, Della distribuzione delle acque nel sottosuolo dell'agro romano e della sua influenza sulla produzione della malaria, the first of many on this topic, Tommasi Crudeli took the question to heart. It is worth quoting his words in support of the theory that cuniculi were excavated to reclaim the Roman Campagna in view of eradicating malaria :
"The tufo of volcanic origin which predominates in the Roman Campagna is permeable to water but is much less permeable than the soil covering it; ... The rain which falls on the hills penetrates rapidly and easily through the layer of soil; ... once it reaches the layer of tufo ... it cannot penetrate it at the same speed. Thus, as soon as there is an increase in rainfall, a considerable quantity of rainwater is held back by the subsoil and tends to accumulate, in varying quantities, between the two layers. Sometimes this water stagnates because the gradient of the surface of the relatively impermeable subsoil (often quite different from the gradient of the surface of the upper layer of soil) forms a sort of basin which holds the water at length. Thus one can often see quagmires on the tops of hills ... Once the rainy season is over, the mud between the permeable and impermeable layers of soil or at the bottom of the hills turns into a swamp where, while the upper layer dries out and cracks, there is enough humidity to create, by means of the combined action of the summer heat and the air which penetrates through the crevices in the soil, an area highly favourable to the production of malaria."
According to Tommasi Crudeli the ancient Romans had several ways of rectifying this condition. On the basis of the writings of Cato (234-149 B.C.) and Columella (active in Rome from 41 B.C.) he refers to the ditches, underground terra-cotta tubes and cuniculi. However, it must be pointed out that neither Cato nor Columella mentioned cuniculi in their writings.
Tommasi Crudeli explored many cuniculi. In one of these near the Via Flaminia just north of Rome, an iron pick used by the ancient excavator was found.3 It was composed of two elongated pyramids joined at their bases. How ironical to think that the network of cuniculi Tommasi Crudeli discovered near Forte Troiani just east of Rome and illustrated as being typical (and most often mentioned by subsequent writers), was not intended for drainage purposes at all. In fact, this complex network of tunnels, the cross-section of which is typical of cuniculi, was connected to a cistern and equipped with a perforated lead panel that filtered the water at the point where the tunnel narrows and enters the cistern.
Tommasi Crudeli later modified his theory on the conditions favouring the spread of malaria. He also gave up the idea that the ancient Romans had excavated cuniculi and claimed that they dated back to a remoter epoch. In his opinion no mention of cuniculi is made in ancient Roman writings on agriculture because they were so well known at that time. In the authors' opinion this does not, however, explain why those writers gave such detailed descriptions of all the other common farming techniques. The theory proposed by Di Tucci and Tommasi Crudeli that cuniculi were drainage works was immediately supported by many famous experts of the day such as the geologists R. Lanciani and G. De Angelis D'Ossat, the French archaeologist M.R. De La Blanchère and much later the agronomist G. Del Pelo Pardi; but it was also tenaciously opposed by the geologist G. Ponzi who maintained that cuniculi had served to collect spring water and A. Celli who considered them works mainly for the purpose of having drinking water.
De La Blanchère, in his entry Cuniculus in the Dictionnaire des antiquités grecques et romaines par Daremberg et Saglio (1877), made cuniculi known abroad as drainage works. In fact, cuniculi were studied as drainage works by other foreign scholars such as T. Ashby, director of the British School at Rome. In the entry he wrote for the 11th edition of the Encyclopedia Britannica on Latium, he dedicated an entire paragraph to cuniculi which was eliminated in subsequent editions of the encyclopedia.
In a long paper published in 1919 in the Bollettino della Reale Società Geografica Italiana, P. Fraccaro made a valid contribution to a clarification of the matter. He stated that the cuniculi in the Roman Campagna were related to a method of searching for water widespread in all Mediterranean countries and beyond on the high plateau of Iran where a very ancient method is still used today. He is referring to the famous kanats (quanat), tunnels excavated, in arid environments, in hills to a depth at which the water table is intercepted. Kanats also have a series of vertical shafts for ventilation and the extraction of debris. This debris, deposited around the lips of the shafts (also to prevent surface water from running off into the shafts), indicates the existence and direction of the kanat below.
Nevertheless the old theory that cuniculi were drainage and land reclamation works is hard to die. A group of archaeologists at the British School at Rome carried out a very detailed study on cuniculi in the early 1960's in which they included a large variety of tunnels having different dimensions, functions and age. They considered the main function of true cuniculi to be the prevention of erosion in the valleys by the collection of water in cuniculi excavated parallel to the axis of the valley and located at the foot of a lateral hill.
In a seminar on the formation of the city in Latium held in Rome in 1977, cuniculi were still being presented as mainly drainage works for land reclamation and, secondarily, as irrigation works.
L. Quilici in his book Roma primitiva e le origini della civiltà laziale (1979) favours the theory that cuniculi were excavated, for the purpose of collecting water from the water table, in Roman times mainly in the late stages of the imperial era.4

2 Several years later it was discovered that malaria (malsania) was not a miasma emitted by damp earth but a disease carried by protozoa whose biological cycle partly takes place in the anofele mosquito which proliferates in a warm environment with stagnant water.

3 Iron was commonly used in Latium from the 8th century onwards.

4 The fact that particularly favourable sites had been inhabited, in some cases for thousands of years can create some confusion when dating constructions or objects made by man in different periods but found today close to one another.

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