It begins about 500 m beyond the nymphaeum of Bergantino, and comes out on the other side in the Mole di Castel Gandolfo locality, where the water flow drove multiple watermills.

[5] According to Titus Livius, this feat of engineering was incited by the Oracle of Delphi: the Roman victory against Veii would be possible only when the lake waters were channeled and used for irrigation.

[7] Dumézil ascribed this story to the Roman custom of projecting religious legendary heritage onto history, considering it to be a festival myth aimed at giving relevance to an exceptional event which would have happened during the Neptunalia.

This legend showed the scope of the powers hidden in waters and the religious importance of their control by man: Veientans too knowing the fact had been digging channels for a long time as recent archaeological finds confirm.

There is a temporal coincidence between the conjuration of the prodigy and the works of derivation[clarification needed] recommended by Palladius and Columella at the time of the canicula, when the waters are at their lowest.