By: Braden Tarrago
All photos included were taken by the author unless otherwise noted
1. Introduction
With its gondola-filled canals, vibrantly-colored buildings, and Instagram-ready photo spots at every turn, the city of Venice, Italy is one of the world’s most popular tourist destinations – and for good reason. No matter where you are in the city or what time of day it is, you’ll always find something that makes you say: “wow, I’m in Venice!”. Upon your entry into the city, immediately after exiting Santa Lucia train station, you are welcomed by a stunning view of the Grand Canal and the Church of St. Simeon Piccolo, seen in Figure 1. But after admiring the view for a few seconds, you might begin to wonder – with all this water, how is this city standing up in the first place? Why does it look the way it does? And what gives it that distinct Venetian feel?
Figure 1: The Church of St. Simeon Piccolo, viewed across the Grand Canal from the exit of Santa Lucia station
Venice possesses a variety of unique characteristics that cause over 35 million tourists to flock to it each year. But in addition to its superficial beauty, Venice is a city that is equally as beautiful behind the scenes. Beyond its picturesque exterior, centuries of careful architectural and engineering planning have combined to make the city into what it is today. Based upon my visit to Venice in September of 2024, this project investigates how engineers and architects responded to the unique structural limitations of this marine city, and how their intentional choices create a unique sense of place, experienced by every soul who steps foot in Venice.
1.1 Historical Background of Venice
Figure 2: Location of Venice, Italy (Foot et al., 2024)
The City of Venice, located in Italy’s northeastern Veneto region (location shown in Figure 2), has a rich and extremely complex history. It is named for the ancient Veneti people who inhabited the region in the 10th century BC (Etymonline, 2017), but its modern history generally begins around the 5th century AD. According to Foot et al. (2024), around this time, Ancient Romans fled to the Venetian Lagoon to escape invasions following the fall of the Western Roman Empire, establishing the foundations of the modern-day city. By the 9th century, Venice developed into a major trading power, gaining autonomy from the Byzantine Empire and establishing its own government. By the 11th century, it became an independent republic, known for its maritime dominance and its unique political system. This republic was led by the Doge, the historical head of the Venetian Republic, whose Palace, seen in Figure 3, is one of Venice’s most famous tourist attractions (Doge’s Palace, 2024).
Figure 3: The Palazzo Ducale, or the Doge’s Palace (Doge’s Palace, 2024)
Later, during the Renaissance, Venice flourished as a center of art and culture, but by the 16th century, its maritime power began to decline due to competition from emerging nations and shifting trade routes. In the late 18th century, Venice was eventually conquered by Napoleon and later came under Austrian rule after the Congress of Vienna in 1815. It was eventually incorporated into the Kingdom of Italy in 1866 during the Italian unification, and has been a part of Italy ever since (Foot et al., 2024).
However, in the 21st century, Venice began to experience a new set of problems. Several major issues are presented by the high volume of tourists that the city receives each year, as well as by climate change. Large cruise ships, although banned by the city since 2021, have caused major issues due to their effects on water levels in the city, as well as due to the powerful waves created by these ships that damage building foundations. In addition, rising sea levels have made Venice even more susceptible to flooding. The massive flood of November 2019 flooded the city in nearly six feet of water, killing two. While these problems are dire and in need of resolution, engineers and scientists are constantly hard at work in search of a solution.
2. Structural Limitations of Venice
As briefly discussed earlier, the City of Venice has a variety of unique structural engineering limitations related not only to its presence in, and around, high volumes of water, but also due to what lies above, below, and around the city. There are three principal structural limitations that are considered in this report.
2.1 Poor Soils
As a whole, the City of Venice sits on very soft and poor soils. According to Foraboschi (2017), below a top layer of mixed garbage, building remains, and other materials, the first true soil layer of the Venetian lagoon is an artificial deposit with average thickness of 2 m, composed of an erratic mix of various silts, loams, clays, and more. From a geotechnical engineering perspective, this means that this top layer is unsuitable for foundations, and as a result, deep foundations must be used to go beyond this layer.
The majority of the lagoon is “characterized by a layer of highly overconsolidated oxidized silty clay, near the ground surface, called ‘caranto’.” The caranto begins on average 4–8 m below the mean sea level and is on average 2-3 m thick – the layer is discontinuous as it has been eroded in many areas due to the high presence of water. Since the caranto is highly overconsolidated, its strength and stiffness are very high, but due to the relative thinness of the caranto layer, it cannot bear high loads (Foraboschi, 2017).
The soil stratigraphy below the caranto is very heterogenous all the way up to depths of 60 m. The soils in this region are mostly cohesive layers, such as clays, loams, and silts, which are generally normally consolidated. Even though the strength and stiffness of the cohesive layers are generally greater than those above the caranto, their values are still relatively low from an absolute perspective. The strength and stiffness of the layers with sand are rather high, but those layers are only a small part of the overall soil profile. Regardless, the average strength and stiffness of the soils below the caranto, up to 10–12 m, are certainly greater than those of the soils above, but only to a moderate extent (while below 12 m they are much greater) (Foraboschi, 2017). As a result of this, piles for building foundations must be driven deep into the soil in an attempt to reach more stable material.
2.2 High presence of water
The defining characteristic of Venice is undoubtedly its canals. Although the Centro Storico of Venice (the historic center of Venice, or the set of islands that are usually colloquially referred to as Venice) may be a majority land, of the entire 410 km2 of Venetian lagoon, only around 8% is land (Mayes, 2015). Unfortunately, this high presence of water presents a variety of issues for the structural integrity of the city.
For one, water infiltration into bricks (of which most Venetian buildings are constructed) compromises their structural integrity, particularly due to the high salinity of the Venetian canal water. Ancient bricks used in Venetian buildings were highly porous, creating ideal conditions for water infiltration and structural damage. The infiltration of this salty water creates internal pressures that eventually induce cracks inside the brick, which leads to localized crumbling or spalling of the brick face (Foraboschi, 2017).
The high water levels also wear away outer plaster layers, exposing bricks to further damage. Especially due to how volatile Venice’s tides are, this has massive destructive potential. As seen in Figure 4, salt deposits are often left on the bricks, showing just how high water levels have come in the past. In addition, the sporadically missing plaster also shows the destructive potential of this salty water.
Figure 4: Exposed brick on a Venetian building with visible salt deposits
Beyond this, the Venetian lagoon is highly susceptible to changes in water level, due to both normal daily tide changes and extreme rainstorms. According to Foraboschi (2017), “It is well known that [the] Venetian lagoon is subject to high variations of water level (daily tidal cycle). The cycle of the tide has a period of approximately 21 h and 30 min, and a difference between high tide and ebb tide that may surpass 1.70 m, with an average value greater than 0.60 m.” Given this baseline susceptibility to water level fluctuation, the potential for storms to affect the water levels in the city is high. During my visit in early September 2024, Venice experienced a major rainstorm for the first time in two months, causing extreme flooding throughout the city. Many canals overflowed (see Figure 5), flooding businesses and making travel throughout the city extremely difficult.
Figure 5: A Venetian canal floods after a rainstorm on September 5, 2024
2.3 Limited space
Venice, as an island city, is obviously limited in land area, with a total footprint of just over 7 km2 (Ratter, n.d.) – less than 3x the total campus area of the University of Washington (University of Washington, 2023). The land area of the lagoon as a whole, as previously mentioned, is small – and is even smaller now than it was in the past. Despite this relative lack of land, Venice still has a relatively high overall population, resulting in a higher population density. As a result, land must be used efficiently, and urban planning is critical. This attitude can be seen in many ways throughout the city. Roads are not built for cars not only for structural reasons, but due to spatial constraints. Pedestrian streets are narrow (see Figure 6), buildings are generally taller than they are wide, and living spaces are only as large as they need to be. In this scenario, it would make sense to build up if you cannot build out – but the previous two constraints make building high relatively challenging. This scenario then begs the question – how do architects and engineers respond?
Figure 6: A pedestrian street in Venice
3. Methods of Response and Their Architectural Effects on Sense of Place
3.1 Foundations
One way that an architectural and engineering response can be seen throughout Venice is through its building foundations. Beginning from the lowest reaches of the building, Venetian foundations are intricate, yet relatively simple. During construction, wooden piles around 5-6 m (16-20 ft) in length were first driven, with hammers, down towards the Caranto layer. There is no consistency in the depth of these foundations from building to building, which is why some buildings across the city have held up better, or settled less, than others. There is also a lack of consistency in the overall length and diameter of these piles, but general estimates can be made. The piles were made out of oak, larch, or pine (How was Venice built?, n.d.) – all woods that are very strong in compression; generally 5000+ psi with the grain (Workshop Companion, 2009).
The reason that these foundations have been able to survive for so long is primarily because of petrification – the continued to exposure to water, nutrients, and an organic environment over a period of several hundred years has petrified (at least some of) the wood into a stone-like substance. These petrified foundations can be extremely strong in compression, but can also be very brittle. Many of these foundations are still standing to this day, and although they are usually hidden, some can be seen throughout the city (see Figure 7). These wooden foundations were then generally overlain by a layer of wooden boards, and then bricks on top (as they are substantially lighter than stone while still maintaining relatively similar strength). The stone blocks visible to the naked eye serve the primary purpose of protecting the bricks from water. These foundations systems are a crucial part of the city and display ancient Venetian engineering still at work thousands of years later.
Figure 7: Exposed wooden piles, similar to those used under Venetian buildings
However, not all Venetian buildings utilize these classic wood-based foundation systems, but the majority do – and those that do not generally have a specific reason for not doing so. Two key examples of buildings that do not have these classical types of foundations are St. Mark’s Campanile (to be discussed shortly), and the Palazzo Nervi Scattolin, the headquarters of the Venice Savings Bank (Šmídek, 2021). The Scattolin, seen in Figure 8, is a rare example of modern (ish) architecture in Venice, and concrete foundations were chosen to fortify the bank’s subgrade vaults and make them less susceptible to settling and other risks associated with wooden foundations. This building will not be discussed in this report for the sake of brevity, but it is undoubtedly an interesting part of Venice’s architectural landscape.
Figure 8: The Palazzo Nervi Scattolin (Šmídek, 2021)
3.2 Columns
Another principal way that an architectural and engineering response can be seen throughout the city is through its use of columns. Columns are a vital part of any structure, playing an essential part in bearing and transferring loads down through a building into the foundations and the ground. However, columns are not the only option to transfer load to the ground – load-bearing walls are also an option, and are also often used. But, in Venice, columns are chosen over walls because, by their nature, columns are weight and space-saving structures that still perform similarly to a wall. This approach is obviously preferable because unlike in most other cities, where suitable foundation material is present in abundance around the site, Venetian structures cannot weigh too much since they are supported by simple pile foundations. Venice is also limited in space, as previously discussed. So, columns are the clear choice for Venice, and they are widely used throughout the city (see Figure 9 for an example).
Figure 9: Corinthian columns used in a Venetian building
But, there was also a clear architectural advantage to using columns. According to Foraboschi (2017), Venetian builders were skilled in geometry and were thus able to use columns to “give a unifying spatial/geometric structure to the whole building”. They used their ability to cut solids into different shapes to blend different approaches to building construction. This allowed them to create a structure composed of thin perforated walls and columns, greatly reducing the overall weight and allowing these impressive structures to be built in an otherwise challenging environment. These builders became even more skilled at dealing with the peculiar structural behavior of Venetian construction, and through their strong community of practice, “every builder [in Venice] picked up the necessary knowledge and awareness to develop [these] skills” (Foraboschi, 2017).
3.3 Arches
One final way that an architectural and engineering response can be seen throughout the city is through the use of arches. Arches are a particularly desirable structural element, previously studied in this class, due to their ability to distribute vertical loads horizontally and control the load path of various loads. The natural shape of an arch directs the force of a load down into the corresponding columns, where it can then be carried into the foundations and ground. Arches are also greatly useful in the horizontal direction, as arches transfer thrust laterally to supports, making them particularly effective for spaces where longer spans are needed, without the need for vertical supports in the middle.
Similarly, arches are also one of the most prominently used architectural features, particularly popular during the Gothic and Renaissance periods. Arches are particularly useful because of their ability to not only add ornateness to a space, but also because of their ability to naturally frame a space, as seen in Figure 10. They provide visual interest and can create a sense of grandeur within a space that otherwise might be relatively mundane. Especially in Venice, where much of the architectural style is homogenous and windows are often simple rectangles, the use of arches emphasizes certain parts of a building, like points of entry, and adds to the overall complexity of a space.
Figure 10: Arches on a Venetian building
4. Case Study: St. Mark’s Square and Campanile
One key location in Venice where the use of foundations, columns, and arches can be analyzed is in St. Mark’s Square (Piazza San Marco), specifically in the plaza itself as well as in St. Mark’s Campanile (bell tower), seen in Figure 11. The current bell tower is actually the second version of the tower – the campanile stood without issue for centuries until 1902, when the previous tower collapsed as a result of careless construction work (Basilica di San Marco, 2019).
Figure 11: St. Mark’s Campanile in St. Mark’s Square, Venice
4.1 Foundations
At the base of St. Mark’s Campanile, thick concrete and stone foundations help keep the building structurally stable. The parts of the foundation shown in Figure 12 are only those visible above the ground of the Plaza, and the majority of the structural elements are below the ground. After the collapse of the original tower in 1902, ensuring that the new foundations were adequate was absolutely a priority for the architects and engineers of the new tower. Ironically, the collapse of the original tower had nothing to do with the failure of the wooden piles on which it stood – after the collapse, the original wooden piles were recovered in perfect shape (How was Venice built?, n.d.). Nonetheless, the new builders decided to err on the side of caution.
Figure 12: The exposed foundation of St. Mark’s Campanile
Reconstruction work on the tower began approximately nine months after the collapse, and the present tower was completed in 1912, 10 years after the original collapse. According to Panwar (2021), the area of the new foundation was nearly doubled from the original 222 m2 up to 407 m2, with new foundation elements being added in addition to the old masonry foundation. Externally, the building was built to look exactly the same, but the inner structural workings were vastly different from the original tower (see Figure 13 for the original plans before the 1902 collapse). Unlike most other buildings in Venice, the new campanile was built using reinforced stone and concrete foundations and supports as opposed to the wooden piles and pure masonry construction that was used before. Although this did result in increased cost, it greatly improved the structural stability of the tower. However, problems developed with this approach as well. In the 1970s and 80s, shear cracks began to develop in the upper foundations (see Figure 14).
Figure 13: Sketch of original plans of St. Mark’s Campanile (Quadri, et. al, 1831)
Figure 14: Shear cracks in the foundation of the bell tower, circa 1970 (Panwar, 2021)
As such, in 2007, an additional reconstruction of the foundation of the campanile began, and prestressed titanium rebars were laid at two levels along the perimeter of the foundation stone blocks. The bars were installed to enhance the flexural stiffness of the foundation and stop the further propagation of cracks (Panwar, 2021). The presence of such a tall and massive structure was particularly complicated by the poor soils underlying the foundation and the presence of relatively high groundwater, which is why intervention with modern structural technology was necessary to keep this building standing.
From an architectural perspective, the foundations anchor the bell tower in the square and provide a visual cue to transition from the grey stone on the floor of the plaza to the striking red brick of the tower. The gradual decrease in size from the lowest level of the foundation bricks to the top provides a visual gradient and brings the massing of the building to life, making it look more like the building grows out of the plaza and less like it was simply just placed there.
4.2 Columns
In the square, there are an almost nauseating number of columns, as seen in Figure 15. These stone columns are important as they carry the load from the building down into the ground without contributing too much extra self-weight. But beyond this, the columns provide a striking sense of order and harmony. They frame the square as a defined gathering space, and the rhythm created by the repetition of columns along the square enhances the feeling of balance. It also draws the eye more towards the focal points of the square, like St. Mark’s Campanile, as these landmarks break up the repetition and monotony of the columns.
Figure 15: The Piazza San Marco
Turning our analysis to St. Mark’s Campanile itself (seen in Figures 11 and 16), the bell tower, standing at 98.6 m (323 ft), is the tallest structure in Venice (Basilica di San Marco, 2019), and is visible from throughout the Square. Having already discussed the foundation system of the current bell tower, and knowing that the history of the structure is anything but ordinary, we turn our attention to further up the building, and we can analyze how the gravity system of the tower functions. Like many other bell towers, the columns of the tower are not distinct from the rest of the tower, but rather appear to blend in.
Figure 16: A view from below St. Mark’s Campanile
In these columns is where engineering and architecture meet yet again. The bell tower utilizes what are called pilasters, which are columns that appear embedded in a wall but are partially exposed. They serve not only to provide critical structural support for the tower, but also serve an aesthetic purpose. Structurally, they provide additional reinforcement and stiffness to the walls of the tower and prevent additional buckling. They also provide texture to the exterior of the building and break up what would otherwise be a flat and relatively windowless surface. And they contribute heavily to the overall form of the structure – the campanile’s vertical form dominates the skyline of Venice and serves as a visual aberration from the horizontal expanse of Piazza San Marco. Its proportions are carefully balanced, with the tower gradually narrowing as it rises. The sheer height of the Campanile also makes it a landmark that can be seen from almost anywhere in the city. The bell tower has long served as a beacon for the city, especially during times when maps were not widely available, as the tower could be used as a landmark in reference to other destinations.
4.3 Arches
Finally, St. Mark’s Square and Campanile are also prime examples of how arches are used. Referring back to Figure 15, in addition to columns, numerous arches are also present in the design of the square. In fact, the columns and arches are intrinsically linked – one could not exist without the other in this case. The arches collect loads from above and transfer them horizontally where they meet the columns, which in turn transfer them downward into the ground. In addition, the high presence of arches in the square again provides harmony and repetition, as well as frames windows through which users of the square can look. In regard to the bell tower itself, arches are also present towards the upper part of the campanile, where the viewing deck is located. These arches frame the view (seen in Figure 17) that visitors get if they ascend the tower; one of the most gorgeous views available of a magical city.
Figure 17: View from St. Mark’s Campanile, looking down onto Piazza San Marco (Deng, 2019)
5. Conclusion and Final Thoughts
After having spent nearly a month in Italy, but only two and a half days in Venice, I know that there is likely a lot I was not able to see. But as an aspiring engineer and architect, I was struck on a deep level by how the interconnection between these two disciplines manifested itself within this city. Architecture and structural engineering are intrinsically linked, in that you cannot have one without the other. It seems like especially in today’s STEM-driven world, there seems to be an implicit differentiation made between these two professions. But without architects, structural engineers would have nothing to make stand up – and without structural engineers, architects couldn’t make their buildings stand up. These two professions are much more similar than many people think – which is why academic programs, like dual M.Arch and M.S. in structural engineering degrees, are growing more popular than ever. The industry is demanding professionals who can speak both “languages”, per se – and it’s up to today’s students to answer the call.
The structural elements discussed in this report – foundations, columns, and arches – are just a few of the key ones that share their background in these two disciplines and that join together to create harmony in the built environment. Beyond providing critical support to buildings, they also make them look nice too. This intersection is where Venice gets its distinctive look from – a carefully crafted blend of architecture and engineering, perfected over centuries. Every city in the world has its own distinctive look, formed by varying usage of basic building elements. It is clear that these basic engineering and architectural elements provide the framework for all of the world’s greatest buildings and landmarks by providing both form and function – and nowhere in the world is this more true than in Venice.
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