Top 10 Medieval Megaprojects

Today we can see great megaprojects being built throughout the world – massive engineering marvels such as airports, tunnels, and skyscrapers. Do we have similar examples from the medieval world?

The megaprojects of the medieval world range from bridges and dams, to the construction of entire cities. Some of these buildings would take generations to finish, and today remain as great landmarks of history. Here is our list of ten of these structures:


1. Land reclamation in The Netherlands

Perhaps the most impressive engineering feat from the Middle Ages has been The Netherlands – more specifically how the people of this country have reclaimed thousands of square kilometres of land from the sea. It was a process that began as early as the eighth century, when settlers in this region would drain coastal lands in order to farm. By the twelfth century these efforts were becoming more coordinated and managed, as systems of dikes were protecting villages and arable lands. There would be setbacks, such as St. Lucia’s Day Flood in 1287, which killed over 50,000 people and created the Zuiderzee, but the land reclamation efforts only continued to expand.

The Dutch people began using windmills in the fifteenth century – they would pump seawater from the land much more efficiently. The process of land reclamation in The Netherlands is a continuous one, but today over 18,000 square kilometres, about half of the country’s land, was once part of the sea.


2. Great Wall of China

While many people associate the Great Wall of China with ancient times, its most well-known sections are actually medieval. China’s history of wall-building dates back to its earliest dynasties, with the main aim of defending its northern borders against pastoral tribes like the Mongols. However, there would be long periods – hundreds of years – where there was no construction of walls, and much of it was allowed to fall into ruin. Then a new dynasty would see value in building these fortifications again.

What we can see today is that China has had numerous megaprojects to create massive wall fortifications. Together, they stretch out to be 21,196 kilometres in total. The most impressive parts are the walls started by the Ming Dynasty in the fourteenth century. They encompass a length of 8,850 kilometres and were largely built of brick and stone as opposed to earlier versions that were largely dirt embankments.

3. Building the city of Baghdad

Most cities around the world are built up gradually, growing over generations to become urban metropolises. However, the founding of the Abbasid city of Baghdad would be conceived of, designed, and built, in just a few years.

Before the Abbasid caliph al-Mansur decided in the year 762 to build his new capital city here, the site was home to a few monasteries. Over a hundred thousand workers and craftsmen were sent to construct the city, which would be round in shape, have four major gates, and be about three kilometres in diameter. The outermost of its triple-walls would be over eighty feet high, and a moat encircled the entire city. Meanwhile, the very centre of the city would be occupied by al-Mansur’s palace and the Great Mosque.


The Round City of Baghdad would be completed in just four years, Suburbs soon emerged around the city, and, being the capital of one of the most powerful empires of the medieval world, it would soon be home to as many as 500,000 people.

4. Lincoln Cathedral

For thousands of years the world’s tallest building was the Great Pyramid in Egypt. But in the early thirteenth century it would be St Paul’s Cathedral in London that gained that title. Then in the year 1311 it would be Lincoln Cathedral, also in England, that became the world’s tallest building when a new spire was constructed. It would reach a height of 160 metres (525 feet).

Many of the cathedrals built in medieval Europe were marvels of engineering, where innovations like flying buttresses would allow these buildings to become very large and spacious. The heights they would reach would certainly make us consider them the skyscrapers of the Middle Ages.


The spire at Lincoln Cathedral would last over two centuries, but when a storm in the year 1548 caused it to collapse, the structure was not rebuilt. It would still remain the tallest structure ever built until the year 1889, when the Eiffel Tower took its place.

5. Naviglio Grande

In terms of engineering, some of the greatest advances made by medieval people were in terms of managing water. One of the best examples of this was the building of Naviglio Grande in Lombardy, which connects the River Ticino to Milan. One of several canals that form an interconnected system around Milian, the Naviglio Grande originally began as a ditch dug in 1157 as part of the city’s defences. However, in 1177 construction began on a canal that would be nearly fifty kilometres long. Using handheld tools, workers continued to expand and widen the canal, and create waterways to irrigate the lands of Lombardy. The project would be completed by 1272, when the entire canal was navigable, but by then over 500 square kilometres of land could now be irrigated by 116 outlets. The canal itself ranges from 12 to 50 metres wide and was supported by several dams. It quickly became a major shipping route and would remain so until the 1970s.

16th century map of River Ticino and Naviglio Grande

6. Pont Saint-Bénézet in Avignon

The building of bridges was often an important task in the medieval world, as they were very useful in making river crossings much quicker and less dangerous. There are many medieval bridges that could make this list, but one of the largest from the period was Pont Saint-Bénézet, which crossed the Rhone River at the French city of Avignon. Legend has it that the first bridge was built between 1177 and 1185 under the direction of a shepherd boy named Bénézet – he was shown a vision from Jesus Christ to build the bridge and even lifted a huge block of stone into the river to serve as the beginning of its foundation.

The first bridge was made of wood and was soon destroyed during a siege. A second bridge was built in 1234 – it would be 900 metres long and span the river through 22 stone arches. The bridge, which was 4.9 metres wide, even curved at places to make use of islands within the river. It would remain in use until the seventeenth century, despite having sections occasionally collapse into the river.

View of the Pont Saint-Bénezet at Avignon from the year 1608.

7. The Nilometer

For millennia the fate of Egypt has been determined by the Nile. Its waters were the lifeline for the country, allowing for farming and trade to take place along the river. It is not surprising that Egyptians were very interested in knowing how much water was exactly flowing down the river, especially between July and November, the annual flood season. Too much water could mean dangerous flooding, while too little would often result in drought and famine.

To get the best information about the Nile River, the Egyptians created the Nilometer, which essentially was a vertical column that could measure the level and clarity of the waters in the Nile. Over time this system became more complex, leading to the building of the Nilometer on the island of Rhoda in Cairo. It was constructed in the year 862 or 863, during the Abbasid Caliphate, and on the outside is a fairly small building, consisting of a pit 13 metres deep, enclosed by an ornate building. However, it also included three tunnels that would bring water from the Nile into its main chamber, where it could be accurately measured using the principle of communicating vessels.

The Nilometer was in use until the end of the 19th century and impressed many medieval visitors. The tenth-century geographer al-Muqaddasi offers this description of how the rising water was measured in cubits:

The rise is not proclaimed until after it has reached twelve cubits, it is announced to the Ruler only, for at twelve cubits the water does not extend to cultivated villages of the countryside. However, when the height of the water reaches fourteen cubits, the lower portion of the region is watered; but if it reaches sixteen, there is a general rejoicing, for there will be a good year. Should it go above that there is fertility and abundance.

The importance of this building to Egypt can be summed up in the fact this is where medieval Cairo’s biggest annual celebration – The Festival of the Opening of the Canal – would begin each year.

8. Salerno’s Aqueduct

One of the great engineering developments of the Roman Empire was the construction of aqueducts, which would bring in water to urban areas. This technology did not disappear during the Middle Ages, as the aqueduct of Salerno in Italy can attest to. Built in the ninth century to bring water to the monastery of San Benedetto, the aqueduct was over 650 metres long, much of it running along arches and pillars that rose 21 metres high.

Interestingly, a story would develop in the Later Middle Ages, in which the aqueduct was said to be built during a single night in the early twelfth century by the scholar Pietro Barliario with the aid of demons. The structure was then called “Ponte del Diavolo”  or ‘Bridge of the Devil’, and would be viewed with superstition for centuries afterward.

The Aqueduct of Salerno – photo by M2m / Wikimedia Commons

9. The Bazacle

The use of water mills grew substantially in the medieval world – for example, the Domesday Book records over 6000 mills in England during the eleventh century. We also know of a variety of methods that were undertaken to improve their productivity. Such was the case upstream of Baghdad where a series of ship mills would be set up in the middle of the Tigris River – these alone were said to have made enough flour to feed 25,000 people a day.

One of the most impressive medieval mega-projects took place in Toulouse, France, where a series of dams were created along the River Garonne in order to channel its waters through dozens of mills. The Bazacle dam dates from at least 1177, was 400 metres long, and was built diagonally across the river. In his book, A History of Engineering in Classical and Medieval Times, Donald Hill explains

Like the other dams it was built by ramming thousands of oak piles about six metres long into the river bed. A series of parallel palisades was thus formed, and the spaces between were filled with earth, wood, gravel and boulders. Breakwaters were built in front of the dam to protect it from floating debris.

The project was owned by The Society of Moulins du Bazacle, which is considered to be Europe’s first joint-stock company. The company was successful for centuries, even after it converted the dams to making hydroelectric power in the nineteenth century.

The Bazacle today in Toulouse. Photo by Don-vip / Wikimedia Commons

10. London’s Conduit

As urban centres grew in medieval Europe, one of the key infrastructure needs would be more fresh water. While the city of London was situated along the Thames River, concerns over how clean this water was, coupled with the growth of the town itself, would lead local officials into looking for a new source for their supply.

In the thirteenth century the city of London bought the rights to a natural spring over four kilometres away, and then had its waters delivered by underground pipes into Cheapside, the heart of the city. Work began on the ‘Great Conduit’ in 1245 – we know that it was working by at least the year 1286, allowing all people to freely access its supply. Records from the City of London reveal that over the years payments were made for its upkeep, rules were put in place on who could use it, and it was even inspected for possible poisoning during the Black Death.

By the end of the fourteenth century the conduit system was expanded, with the pipes carrying the waters further into the city. The buildings that housed the conduits were even used to mark celebrations, such as when King Henry V returned after his victory at the Battle of Agincourt in 1415. The water conduit would be in use until the Great Fire of London in 1666.

A 19th century depiction of the Cheapside Cross, with the Great Conduit to the right of it.

There are many more examples of large and small-scale engineering and construction projects from the Middle Ages. You can learn more from Donald Hill’s book A History of Engineering in Classical and Medieval Times.

Top Image: The Great Wall of China – photo by Hao Wei / Wikimedia Commons