Venice was built on the edge of the Adriatic Sea on 118 islands in the middle of the Venetian lagoon, which is composed of reeds, mud and swamps.
Along with stabilization and then a drop in sea level, the invasion of the Huns and after the Ostrogoth in Italy brought the first refugees to the inhospitable place. But it was especially the arrival of the Lombards in 568 in the region of Vicenza, Verona, Treviso and Padua, that triggered a massive migration towards the coast. The islets in the lagoon of Venice proved inviolable. The Roman population fled before the invader, sometimes in disarray, sometimes behind the clergy and their leaders.
In short, the establishment was first disseminated, spread over a large number of small agglomerations, each community separating itself, isolated from the others. Some habitats were precarious; others seemed to be better anchored, as in Torcello. This population, coming from the continent, found in these muddy islands the protection of the lagoon environment in which the horses of the barbarians could not reach.
Insecurity on dry land prevented refugees from returning, and refugees were forced to form a new city in the lagoon, planting thousands of stakes in the mud and covering the islands with wooden floors. Development work was carried out: the banks were consolidated, the floors were drained, wooden houses and brick or stone monuments were built with materials sought on land.
How was Venice built?
For a long time, Venice was believed to be in a forest of tree trunks. However, this is only partially true: the city lies on the sandy and muddy terrain of the numerous islands. The foundations on which the walls of palaces and churches were built are generally four parallel rows of walls perpendicular to the canal, which were built up to 80 centimeters deep in the ground.
Only the façades on the side of the canal rest on tree trunks: to prevent the walls from falling, posts three meters long, made of oak, alder or poplar, were thrown to the ground, each half a meter away. The gaps were then filled with clay and silt, thus forming a solid base.
To prevent the wood from rotting, this block of wood and clay needed to be completely underwater. The buildings are largely made of wood, limestone and clay bricks. This special construction is so stable that it has survived for centuries.
However, buildings are threatened by water. Venice threatens to sink into the lagoon. Because the islands’ sandy and muddy subsoil, on which the foundations are located, gives way under the enormous weight of the buildings. The city sinks a few millimeters a year – a total of 23 centimeters in the past hundred years. Many ground floors are no longer habitable.