‘Well-cisterns’ of Roman period indicate navigation routes and landscape modifications in the lagoon of Venice and along the north-eastern Adriatic coast.

Underwater investigations in the lagoon of Venice have permitted to interpret a structure made of bricks of Roman period as a partially preserved well-cistern . This structure is indeed very similar to another, better-preserved cistern excavated in the same area. The analysis of mortars, the evaluation of the depth of the structure base in respect to relative sea level, and the absence of foundation poles in the underlying soft lagoon mud support such interpretation. Our results confute the previous interpretation of this structure as a tower. A comparison with other poorly-studied Roman structures of the same type located along the North Adriatic littoral, suggests that they were probably used to supply the ships of fresh water. In the Middle Age, similar artefacts were used in the islands of the lagoon for the sustenance of the citizens and became a characteristic of the small squares (campi) of Venice. The analysis of the Roman cisterns of Canale San Felice tidal channel and adjoining pier confirm the importance of investigating these infrastructures in order to gain a better understanding of inland navigation routes along the upper Adriatic lagoons.