Why Was Venice Built on Water? — The Venetian Lagoon, the Rise of a Maritime City, and Its Modern Crisis

 

Venice, the City Built on Water

One city that is hard to leave out of any trip to Italy is Venice.

With canals winding through narrow streets and gondolas and boats gliding across the water, the entire city can seem as if it were floating on the sea.

Looking at the magnificent scenery of St. Mark’s Square, grand churches, and centuries-old palaces, one question naturally comes to mind.

Italy has plenty of solid land, so why did people choose to build a city here, in a landscape where shallow seawater, tidal flats, and small islands meet?

To understand the answer, we need to look beyond the magnificent Venice we see today and travel back about 1,500 years, to a time when Italy was experiencing profound political turmoil.

1. Venice Was Not Originally an Ideal Place to Live

The city of Venice stands within the Venetian Lagoon.

A lagoon is not a lake completely separated from the sea. Instead, it is a shallow body of water partially separated from the open sea by features such as barrier islands and sandbars.

The Venetian Lagoon and Its Mudflats

Today, the Venetian Lagoon may appear beautiful to visitors, but from the perspective of people living in ancient times and the early Middle Ages, it was hardly an ideal place for farming or building a large city.

The land was low-lying and waterlogged, and solid bedrock was difficult to reach.

Paradoxically, however, this inhospitable landscape would eventually become one of Venice’s greatest advantages.

2. Seeking Refuge in the Lagoon

Around the fifth century, during the final decades of the Western Roman Empire, northern Italy fell into a period of profound turmoil.

The Huns and other invading groups entered Italy, and warfare and political instability continued even after the collapse of the Western Roman Empire.

Amid this upheaval, some inhabitants of northeastern Italy moved to the islands of the lagoon, which were relatively difficult for invading forces to reach (UNESCO World Heritage Centre, n.d.).

Seeking Refuge in the Venetian Lagoon

For armies moving across the mainland, open plains and roads provided relatively easy routes of travel.

The lagoon, however, was a very different environment.

Its shallow waters, tidal flats, and intricate network of channels made it difficult for large land-based armies to approach.

In other words, the same landscape that made farming and urban construction difficult also offered protection from outside attacks.

The history of Venice thus began in this unusual space between land and sea.

3. But How Could a City Be Built on Mud?

That created another problem.

The lagoon may have provided refuge from enemies, but constructing heavy stone buildings on its soft, waterlogged ground was far from easy.

To overcome this challenge, the Venetians developed distinctive foundation-building techniques.

Thousands of wooden piles were driven closely together into the ground beneath construction sites to strengthen and stabilize the foundations.

Various types of timber were used, including alder, larch, and oak. Wooden platforms and layers of stone were then placed above the piles, creating a stable foundation on which buildings could be constructed (Macchioni et al., 2016).

Building a City on Mud — Venice’s Wooden Pile Foundations

Many of the churches and palaces we see in Venice today stand on foundations constructed using this technique.

In other words, beneath Venice’s magnificent stone city lies another city hidden from view:

a vast forest of wooden piles driven deep into the waterlogged sediments and mud below.

4. Why Didn’t the Wooden Piles Rot Away?

This raises another intriguing question.

If the wooden piles were submerged in water, how could they continue supporting buildings for centuries?

The key is oxygen.

Oxygen and microorganisms play important roles in the decomposition of wood.

However, when wooden piles are driven deep into waterlogged sediments where the supply of oxygen is severely limited, the activity of organisms responsible for decomposing the wood is also greatly reduced.

As a result, the timber can survive for far longer than it would if it were exposed to air (Bernabei et al., 2019).

Venice’s Wooden Piles Preserved in Oxygen-Poor Sediments

It is sometimes said that Venice’s wooden piles have “turned to stone” underwater, but this description is misleading. The timber did not simply become completely petrified.

It is more accurate to understand that the wood has remained relatively well preserved for long periods because of the oxygen-poor conditions surrounding it.

Thanks to this foundation-building technique, the Venetians were able to construct massive buildings even on the soft ground of the lagoon.

5. How Venice Turned a Geographic Disadvantage into an Advantage

The lagoon initially provided refuge from invasion, but over time, the Venetians began to make active use of this unusual geographic environment.

The shallow lagoon, difficult for land-based armies to penetrate, offered a natural defensive advantage. At the same time, its waterways provided direct access to the sea, creating favorable conditions for maritime trade.

Through the Adriatic Sea, Venice expanded into the Mediterranean and developed an extensive maritime trading network connecting the eastern Mediterranean with Europe.

Venice: From a Lagoon Settlement to a Center of Mediterranean Maritime Trade

By the late Middle Ages, Venice was no longer simply a settlement founded by people seeking refuge.

It had developed into the powerful Republic of Venice, supported by a formidable navy and an extensive commercial network.

The lagoon environment that had initially seemed like a geographic disadvantage ultimately became one of the foundations that enabled Venice to emerge as a powerful maritime city at the heart of Mediterranean trade.

The Port of Venice at the Height of the Renaissance

6. But Now the Sea Is Threatening Venice

Ironically, the sea that once protected Venice and helped it prosper has now become a growing threat to the city.

One of the most prominent challenges is Acqua Alta, the phenomenon of exceptionally high tides that can flood low-lying areas of Venice.

Acqua Alta Flooding in Venice

Acqua Alta refers to episodes of exceptionally high water levels in Venice.

Especially during autumn and winter, a combination of high tides, atmospheric pressure, winds, and other meteorological and oceanographic conditions can push water from the Adriatic Sea into the Venetian Lagoon, flooding low-lying parts of the city (Faranda et al., 2023).

St. Mark’s Square (Piazza San Marco) is particularly vulnerable because it is one of the lowest-lying areas of Venice.

When the water rises, temporary elevated walkways may be installed for pedestrians, creating the distinctive sight of people crossing the flooded square in rubber boots.

St. Mark’s Square Flooded by Acqua Alta

7. Is Venice Really Sinking?

Venice’s problem is not simply that sea levels are rising.

The region has experienced natural land subsidence over a long period, while groundwater extraction in nearby industrial areas during the twentieth century further accelerated the sinking of the land. This human-induced effect was greatly reduced after groundwater extraction was restricted (Tosi et al., 2013).

However, long-term sea-level rise remains a major challenge.

To understand Venice’s vulnerability, therefore, we need to consider both processes together: the gradual lowering of the land relative to the sea and the continuing rise in sea level.

To protect the city, Italy developed the MOSE (Modulo Sperimentale Elettromeccanico) project, a system of large movable barriers installed at the entrances connecting the Venetian Lagoon with the Adriatic Sea. The system is now used during extreme high-water events to help protect Venice from flooding.

The MOSE Project: Protecting Venice from Rising Sea Levels

However, if sea levels continue to rise over the long term, how effectively Venice can continue to protect itself will remain an important challenge for the future.

Conclusion — A City That Turned Geographic Disadvantages into Strengths

Looking back at the history of Venice, it becomes clear that the city is much more than a beautiful tourist destination.

One of the reasons people initially sought refuge in the lagoon was to escape threats from the outside.

Building a city in an environment dominated by mud and water was extremely difficult, but the Venetians adapted by reinforcing the soft ground with thousands of wooden piles.

The lagoon and the sea that had once helped protect the settlement from invasion later connected Venice to the vast maritime trading networks of the Mediterranean.

An inhospitable lagoon that people had once chosen as a place of refuge ultimately gave rise to one of the world’s great maritime cities.

Today, however, the sea that once protected Venice has become a source of growing danger.

Venice therefore offers a remarkable example of how humans have adapted to challenging natural environments to build and sustain cities. At the same time, it illustrates a new challenge facing coastal cities around the world: how to respond to environmental change and rising sea levels.

If you ever take a gondola through the canals of Venice, it may be worth looking beyond the magnificent palaces and imagining what lies beneath them.

Deep in the waterlogged sediments below your feet are countless wooden piles that have supported the city for centuries—and the history of people who transformed the sea from a place of refuge into the foundation of their way of life.

Gondola Tours, One of Venice’s Most Iconic Tourist Attractions

References

Bernabei, M., Macchioni, N., Pizzo, B., Sozzi, L., Lazzeri, S., Fiorentino, L., Pecoraro, E., Quarta, G., & Calcagnile, L. (2019). The wooden foundations of Rialto Bridge (Ponte di Rialto) in Venice: Technological characterisation and dating. Journal of Cultural Heritage, 36, 85–93. https://doi.org/10.1016/j.culher.2018.07.015

Faranda, D., Ginesta, M., Alberti, T., Coppola, E., & Anzidei, M. (2023). Attributing Venice Acqua Alta events to a changing climate and evaluating the efficacy of MoSE adaptation strategy. npj Climate and Atmospheric Science, 6, 181. https://doi.org/10.1038/s41612-023-00513-0

Macchioni, N., Pizzo, B., Capretti, C., Giachi, G., Sozzi, L., & Lazzeri, S. (2016). An investigation into preservation of wood from Venice foundations. Construction and Building Materials, 111, 652–661. https://doi.org/10.1016/j.conbuildmat.2016.02.144

Tosi, L., Teatini, P., & Strozzi, T. (2013). Natural versus anthropogenic subsidence of Venice. Scientific Reports, 3, 2710. https://doi.org/10.1038/srep02710

UNESCO World Heritage Centre. (n.d.). Venice and its Lagoon.