Primo contributo al censimento delle cavità sotterranee di Viterbo

Viterbo, like other ancient cities and villages of Lazio that have been developed on pyroclastic units, has a rich subsoil of underground man-made cavities in its millennial history. These cavities are mainly concentrated in the old town, but they also extend into peripheral areas and even into agricultural areas. The shapes and dimensions of these underground environments are varied. They range from narrow tunnels, presumably connected to hydraulic works of Etruscan and Roman times or to escape routes and secret passages of the Middle Ages, to large environments, often altered remains of Etruscan tombs, Roman cisterns, dovecotes, medieval “butti”, etc. In modern and contemporary times, these environments have been repeatedly reused for various purposes: cellars, warehouses, shelters, etc. With the beginning of the Second World War, starting from the Royal Decree of 24 September 1936-XV n. 2121, many cavities were enlarged to be used as air-raid shelters, but in the immediate aftermath of the war, they were closed to counter the black market and other illegal activities that proliferated there. The entrances to the shelters, the passages, and tunnels that allowed access to other underground environments were walled up, with the result of losing almost completely their memory. This underground uni- verse has been abandoned to degradation for decades, frequented and known only by illegal tomb raiders, or people interested in the disposal of aggregates or other types of waste. Without control and maintenance, some of those cavities were subject to collapse, thus blocking access, and leading sometimes to the opening of sinkholes, with danger to the infrastructure and to the homes. In recent years, thanks to the efforts of some speleological groups, archaeologists, geologists, and some associations, it has been possible to rediscover some of these cavity systems, and to open to the public a small part of the Viterbo Underground circuit.3n