Lake Fucinus (central Italy)

Claudius had a mountain between Lake Fucinus and the river Liris tunneled through, in order to drain the water and gain land. The work lasted eleven years and employed thirty thousand men (Suetonius, Claudius 20). Before the outlet was opened, the emperor staged a naval battle here: according to Tacitus nineteen thousand condemned men fought (Annals 12.56).

The tunnel turned out to be too shallow and had to be deepened (12.57). The lake was drained completely only in the 19th century.