Their arid country was the best safeguard of their cherished liberty; for the bottle-shaped cisterns for rain-water which they excavated in the rocky or argillaceous soil were carefully concealed from invaders.
The existence of numerous ancient cisterns shows that in Roman as in modern times rain-water was largely used for lack of springs.
The aqueduct was constructed in quite recent times, rain-water having previously given the only supply.
Under the republic, and until modern times, the water supply of Venice was furnished by the storage of rain-water supplemented by water brought from the Brenta in boats.
The famous Venetian pozzi, or wells for storing rain-water from the roofs and streets, consisted of a closed basin with a water-tight stratum of clay at the bottom, upon which a slab of stone was laid; a brick shaft of radiating bricks laid in a permeable jointing material of clay and sand was then built.