It is fed by snow meltwater and the seasonal ancient water level variation is estimated to be typically 12 m. The Marsi, the local inhabitants, had made petitions to Rome to control the unstable level of the lake which very often flooded villages because of the frequent cloggings of the only natural swallow-hole at Petogna near Luco dei Marsi.

In summer because of the receding waters, the lands surrounding the inhabited areas often became marshy causing serious health problems due to malaria.

[7] In 41 AD[1] Emperor Claudius resumed the ambitious plan and, thanks to substantial public financing, entrusted a Roman enterprise with the works.

The easiest plan was to dig the shortest tunnel through the low Cesolino hill and into the Salto River and eventually into the Tiber.

The tunnel had to be designed to be the shortest compatible with a very shallow slope and in a compass direction that ensured it entered the Liri river at a level lower than the lake, a remarkable feat considering the instruments of the time.

Accidents during the construction included several landslides in the most vulnerable and sandiest sections and in the dam between the mouth of the tunnel near the Fucine inlet.

The economy of Marsica and especially of the cities of Alba Fucens, Lucus Angitiae and Marruvium thrived and the surrounding mountainous areas became popular as holiday resorts.

[19] With the fall of the Roman Empire and the Barbarian invasions maintenance inevitably failed and also because of a serious earthquake in 508 AD,[20] the canal was clogged with the consequent return of the Fucine Lake to its previous levels.

In June 1977, with the aim of protecting and exploiting the work, the Archaeological Park of Claudius was established, between the entrances to the tunnels and the Fucine Inlet.