Tunnels of Claudius: Ancient Roman Hydraulic Engineering near Avezzano

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Country: Italy

Civilization: Roman

Remains: Infrastructure

History

The Tunnels of Claudius are located near Avezzano in the province of L’Aquila, within the Abruzzo region of central Italy. This extensive hydraulic system was built by the ancient Romans during the reign of Emperor Claudius between 41 and 52 AD. Its primary purpose was to partially drain Lake Fucine, a large lake prone to flooding, to protect the local Marsi communities and convert marshy lands into fertile fields.

The idea to drain Lake Fucine was first proposed by Julius Caesar, but his assassination prevented its realization. Claudius revived the project with significant public funding, choosing to construct a long tunnel through Mount Salviano to channel water safely into the Liri River. This route avoided flooding risks to Rome. The construction involved about 30,000 workers and slaves and was one of the most ambitious engineering projects of the Roman era. Claudius celebrated the completion in 52 AD with a staged naval battle on the lake, attended by his wife Agrippina and the young Nero.

Following Claudius, emperors Trajan and Hadrian maintained and repaired the tunnels, improving their efficiency. Their efforts reduced the lake’s surface by roughly 6,000 hectares, which enhanced local agriculture and made the surrounding mountains attractive as resorts. However, after the fall of the Roman Empire, upkeep stopped. The tunnels gradually clogged, especially after a major earthquake in 508 AD, causing the lake to return to its original size.

In the medieval period, attempts to restore the drainage system were made by Frederick II in the 13th century and later by Ferdinand IV in 1790. Both efforts failed due to financial and technical challenges. The project was revived in 1854 by Alessandro Torlonia, who renovated and enlarged the original Roman tunnels with the help of engineers Franz Mayor de Montricher, Henry Samuel Bermont, and Alexandre Brisse. By 1878, the lake was fully drained, transforming the basin into productive farmland.

In the early 20th century, the Torlonia family built a second emissary tunnel to support the main one during maintenance. The entire system was declared a national monument in 1902. In 1977, the Archaeological Park of Claudius was established to protect the site, which gained further recognition in 2016 when the Italian environmental organization FAI named it a “Place of the Heart.” Efforts continue to preserve and promote this remarkable example of ancient hydraulic engineering.

Remains

The Tunnels of Claudius consist of a main emissary tunnel over six kilometers long, designed to drain water from Lake Fucine to the Liri River. The tunnel’s cross-section varies between five and ten square meters, with a gentle slope allowing water to flow steadily. The system begins at the Incile del Fucino near Avezzano, where a collector canal gathers water from surrounding streams. This entrance area includes two water basins and three sluice gates to regulate the flow.

The Incile is marked by a neoclassical stone statue of the Immaculate Conception of the Virgin Mary, created in 1876 by architect Carlo Nicola Carnevali. This monument stands as a later addition reflecting 19th-century restoration efforts. The main tunnel passes through Mount Salviano and ends beneath the town of Capistrello, where water discharges into the Liri River.

Supporting the main tunnel are six inclined service tunnels, called cunicoli, and 32 vertical wells. These wells served as ventilation shafts, access points for workers, and channels to remove excavated material during construction. Their depths range from 19 to 122 meters, with the deepest wells located on the western slope of Mount Salviano. The cunicoli include the Cunicolo Maggiore (Major Tunnel) on the eastern slope, notable for its three large entrance arches and an oblique bypass tunnel. The walls here were built using the “fori pontai” technique, a Roman method involving holes for scaffolding.

Other service tunnels include the Cunicolo del Ferraro (Blacksmith Tunnel), partially paved and lit, connected to the Major Tunnel by the bypass. It is named after blacksmiths who worked nearby during construction. The Cunicolo Imperiale (Imperial Tunnel) lies slightly lower and connects to one of the wells. The Cunicoli del Calderaro, della Macchina, and della Lucerna (Coppersmith, Machine, and Oil-Lamp Tunnels) are located on the western and southern sides of the Palentini fields and Mount Salviano, linking various wells.

Some sections of the tunnels still preserve original Roman masonry in opus reticulatum, a net-like pattern of stonework, especially near the entrance and exit points. The tunnels pass through varied geological formations, including loose rock and sandy areas, which required scaffolding and structural supports during construction. Remnants of these supports were uncovered during the 19th-century restoration.

The 19th-century renovation by the Torlonia family enlarged the tunnel sections and added new ventilation shafts and service tunnels. While following the original Roman layout closely, this work led to the loss of some superficial Roman features. The site also includes a collector canal and a reservoir known as the “Bacinetto,” a depression used to store water and facilitate maintenance.

Today, the entire system is protected within the Archaeological Park of Claudius. It remains an important archaeological and speleological site, preserving the legacy of one of ancient Rome’s most impressive hydraulic engineering achievements.