Ancient history

Venice:how to build a city on water

View of one of the many canals serving as "streets" in Venice • ISTOCKPHOTO

One of the major challenges of the Venetians consisted in building an urban ensemble on what was previously only a mosaic of islands and islets on often marshy ground. To do this, they developed a technique to lay the foundations of buildings using wooden piles, a layer of impermeable stone and larch platforms. The resistance of many buildings shows that, several centuries later, this method still proves its worth. The urban structure of Venice was articulated around squares, the campi or campielli , a name inherited from the time when these spaces were used as pastures or vegetable gardens. Over time, these squares were paved and surrounded by shops and warehouses. On every campo stood a church whose facade generally faced a canal. In the center of the square was dug a well whose coping, often very decorated, marked the importance of drinking water for the survival of the population. Laws protected the purity of the water and prohibited "animals, dirty hands or vessels" from approaching it.

The foundations
The subsoil of the lagoon is made up of caranto , a succession of layers of sand and compressed clay. The builders drove into it wooden piles firmly held together, the length of which could reach 7.5 meters. The very low oxygen content of caranto prevented these pilings from rotting. Then the architects placed on this solid base a layer of Istrian stone, which was used to waterproof the construction.

It was only at the end of the 19th th century that an aqueduct linked the "Terra Firma" to Venice. Until then, the city was supplied with rainwater collected on the squares by means of gutters. This water then passed through a series of filters intended to purify it, before flowing into a cistern located in the center of the square. This central well, several meters deep, had walls of impermeable clay.

Bridges and Canals
The authorities regularly dredged the bottom of the canals to prevent the debris that accumulated there from clogging them. To cross the canals, you had to cross privately owned bridges and pay a toll. To build the stone bridges, the canal was first drained, the banks of which were then consolidated with pilings, and then the bed was lined with stones.