Located in Abruzzo, near L'Aquila, Lacus Fucinus was the third largest lake in Italy, covering 54 square miles. the Emperor Claudius undertook an ambitious project to drain out a portion of the lake to create arable farmland. According to Suetonius (Claudius 20), the enterprise was legendary, with 30,000 men working 11 years to create a 3.5 mile long tunnel, reached by a series of entry tunnels, one of which is visible in the video below. It was a difficult labor; Cassius Dio (Book LXI.33.5) records one collapsed tunnel and issues of embezzled funds by Claudius' freedman Tiberius Claudius Narcissus. Hadrian later widened and deepened the tunnel, to create more arable land, but in Roman times, the genius of the project was to allow part of the lake to exist alongside the numerous villages along the banks. After many later attempts to drain the lake the Torlonia family was successful in 1877, finally destroying forever the relationship between the many townships that once populated the lakeshore.
Darius Arya streams from the Fucine Lake going into detail about the impressive engineering works