During the reign of Nero (54-68 CE), a plan appeared to dig a 257 km long water canal from Lake Avernus, near Puteoli (Pozzuoli), to the vicinity of Rome. The idea was to secure grain supplies to the capital, as ships often crashed in the final stretch between Puteoli and Rome. Established during the rule of Claudius (41-54 CE), the new port at the mouth of the Tiber meant that many ships were pushed back by storms onto the built embankments and fortifications.
The Roman historian Suetonius is sceptical about the whole initiative and rather considers it a manifestation of Nero’s megalomania.
He also began a pool, extending from Misenum to the lake of Avernus, roofed over and enclosed in colonnades, into which he planned to turn all the hot springs in every part of Baiae; a canal from Avernus all the way to Ostia, to enable the journey to be made by ship yet not by sea; its length was to be a hundred and sixty miles and its breadth sufficient to allows ships with five banks of oars to pass each other. For the execution of these projects he had given orders that the prisoners all over the empire should be transported to Italy, and that those who were convicted even of capital crimes should be punished in no other way than by sentence to this work.
– Suetonius, Nero, 31
It would certainly be an expensive operation – the canal’s route would lead through the Pontic marshes; the channel would be connected to the rivers Volturnus and Liris; a lot of work, in particular, would require digging tunnels in mountainous areas. It should be noted, however, that the solution could certainly shorten the delivery of goods to the capital and secure them.
After the fall of Nero in 68 CE, the idea was abandoned. Instead, during the reign of Domitian (81-96 CE) a road was created via Domitiana (between Sinuessa and Puteoli); and in the reign of Trajan (98-117 CE) enlarged Portus over the Tyrrhenian Sea.