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7 Incredible Never-Built French Engineering Marvels

Ryan spent time in France as a teaching assistant. He has an interest in French history and architecture and likes to relay his knowledge.

Corbusier's Plan Voisin for Paris would have been truly nightmarish, but is a perfect example of some of the never-built French engineering projects

Corbusier's Plan Voisin for Paris would have been truly nightmarish, but is a perfect example of some of the never-built French engineering projects

France is a country renowned for the accomplishments of its engineers, buildings, and architects. Versailles, the Eiffel Tower, the Suez Canal, the Louvre, the Statute of Liberty, the Canal du Midi, the Chateau de Chambord, the Guiana Space Launcher Center, the Maginot Line, the Hausmanization of Paris, the Arc de Triomphe, the fortresses of Vauban, the Champs Elyséess, the Millau Viaduct—the list seems almost endless! But even in France, with its famous engineering tradition and the genius of French engineers backed by the grandeur of an interventionist state, there are still grand projects and buildings left behind - either on the drawing board or never completed. Massive skyscrapers, canals, aqueducts, flooding projects. If even for France these were too much, they must have been staggering indeed!

The partially completed Aqueduc de Maintenon

The partially completed Aqueduc de Maintenon

1 - Aqueduc de Maintenon

Louis XIV, the Sun King, was a great builder, a king who strove with his every fiber for his prestige and gloire. Versailles stands today as an enduring testament to the Sun King, a massive show of state power, authority, elegance, luxury, and refinement. Most famous elements are the great gardens and the monumental fountains which ornament this vast ode to the ambitions of France's most splendid king—and which have an unquenchable thirst for water, tremendously difficult to provision in the 17th century, with up to 1,400 fountains and jets at its peak, and at the end of the reign of Louis XIV, they could consume a staggering 6,300 cubic meters of water per hour.

The fountains of Versailles consumed water like Louis XIV consumed men and money for his wars and state

The fountains of Versailles consumed water like Louis XIV consumed men and money for his wars and state

Something had to be done to provision lofty Versailles, located high above surrounding waterways, 142 meters above the Seine, and several kilometers away to boot. Only the Clagny pool somewhat to the north of Versailles, today filled in, could supply water for the chateau immediately—but its water supplies were very limited, with just a few streams. Some immediate proposals were able to supply a few hundred cubic meters per day, by horse and windpower from surrounding pools, but for Louis XIV, this was far from enough.

The initial solution was in-and-of-itself a marvel of 17th-century engineering: the Machine de Marly. This elaborate contraption, designed by the Walloon engineer Arnold de Ville, was a complex, water-wheel (no loss than 14!) driven pumping station, designed to lift water from the Seine up to insatiable Versailles. The machine was an incredible feat of engineering, and in service for 133 years between 1682 and 1817, it permitted up to 5000 cubic meters per day when it was initially constructed, pumping water up over 150 meters over a 700 meter slope, to then be sent by the Aqueduct of Louveciennes to Versailles. Unfortunately, despite the real improvement that the machine permitted, it had some drawbacks - it was very unreliable with all of its complex pipes, waterwheels, and pumps (and required constant maintenance since much of it was built of wood) so that the amount of water transported fell over time, and it was one of the noisiest machines in the world. A better solution was needed.

The Machine de Marly

The Machine de Marly

An obvious fix was simply to take water from a higher elevation, so that it could flow to Versailles by gravity. An aqueduct on a grand scale, much like the Romans of yesteryear, whose impressive arches dotted Europe, often still in use in former territories of the Roman Empire - such as at Nîmes in France. But to build an aqueduct to Versailles would be a major effort: after the most immediate sources such as the ponds at Trappes and the Bois d'Arcy were tapped, and the Aqueduc de Buc built from the Saclay Plateau, as well as the Loire aqueduct shown to be impractical due to a lower elevation than Versailles, the solution chosen was to access water from the Eure river. But this was some 80 kilometers away, and there was the formidable Eure Valley itself to cross, 40 kilometers into the aqueduct's path. Ironically, it would both be the reason for why the aqueduct failed to be completed and why it was so impressive that it merits a spot on this list.

The half-completed aqueduct today

The half-completed aqueduct today

Louvois, French minister of war and after the death of Colbert in charge of the king's palaces and buildings, initially planned a massive, 17 kilometer long aqueduct with three tiers of arches, reaching a height of 72 meters. Vauban, the redoutable French engineer, siege expert, reformer, and general, would design rather less grandiose plans by contrast: more parsimonious with the royal funds, he desired a syphon aqueduct, a "crawling aqueduct" as he called it, which would rely upon water pressure to cross the valley. Vauban managed to trim Louvois' project down to two aqueducts, with the one crossing the Eure being 5 kilometers long, with a single tier of arches, but in any case this still repesented a huge investment.

Nevertheless, construction started in May, 1685, using thousands of French royal troops as well as civilian labor—with up to 1/10 of the French army employed at any one time. Soldiers were much cheaper than civilians, and with labor forces of up to 22,000 soldiers at work, not counting the civilian laborers who brought the total up to nearly 30,000, this must have counted quite a lot! Unfortunately for these poor souls, the worksite was in a swampy low ground, and up to 6,000 died of diseases, principally malaria. The death toll as a whole reached 10,000.

A map of the canal

A map of the canal

And unfortunately, it would all be for naught! In 1688, 3 years after construction began, the Nine Years' War broke out, and France had far more important things to worry about and to use 1/10th of its prewar army on than building Versaille's water supplies, with a brutal fight for survival on its Eastern borders. The canal was cancelled, and its construction abandoned. One can still see the massive aqueduct even today.


2 - Trans-Saharan Railroad

France's African colonial empire had two principal zones: French Northern, and French Western Africa. Although by the 1900s, France formally owned all of the territory in between, this was the thoroughly desolate, almost impassible, stretch of burning sand and rock called the Sahara desert. Any movement between the two would rely, other than a few experimental crossings and a short-lived bus route in the 1930s, on aircraft and on the French merchant marine.

Uniting these two disparate colonies was a fixation for French colonial administrators and planners, and from the 1870s onwards various parliamentary discussions and reports were organized about building a railroad which would cross the Sahara, with the typical plan calling for it to stretch between Algiers in the North and Dakar in the Southwest, the two capitals of the French colonial territories. Engineers developed proposals for building the line, and in French West Africa part of the reason for why rail lines were pushed up to Bamakao was to prepare for the Trans-Saharan railroad, but there were major obstacles in the way. There was a severe lack of water along the route, necessary for cooling down the locomotives—particularly if they were steam powered—and the incredible, burning heat would make maintenance, repair, upkeep, and above all lese construction very difficult. The terrain was difficult, with sand, rocks, and major dunes, and the distance to cover, thousands of kilometers, combined with this to make it tremendously expensive. To top it all, the project was economically dubious in the extreme - after all, even when completed transport by sea would probably still be more competitive, and the trade routes were of both limited importance to the French economy and limited absolute size. There was no real reason to proceed with the railroad other than for prestige or strategic reasons, and there were always more pressing priorities.

When WW2 broke out, the decision was made to extend the existing rail lines in North Africa to Kenadsa, in Southern Oran, in order to better access the coal mines there. The work was incredibly hard, and relied largely on interned Spanish Republican prisoners of war, working in rudimentary conditions, in temperatures which reached 40 degrees Celsius in the shade, with limited and hot water, and with terrible primitive living conditions: this gave rise to terrible health and diseases among the workers.

When France fell to the Germans in 1940, ambitions became much larger. A new, right-wing, anti-parliamentarian, authoritarian government came to power in France, under the leadership of Marshal Pétain. Vichy pulled France—as best as it could—out of the war and collaborated with the Germans. Vichy had two continuing trump cards in its deck - the powerful French fleet, and the massive French colonial empire, which was vital for its vision of national revival, developing the resources of the colonies to rebuild French power. Both North Africa and West Africa, as well as the overwhelming majority of the pre-war French colonial empire, had rallied to Vichy, and Vichy wished to bind the empire together, strengthen it, use it as propaganda for a renaissance, and use it to continue to claim some sort of great power status. Furthermore, Vichy also wished to show itself as decisive, firm, visionary, in contrast to the unstable parliamentary mess of the 3rd Republic. Thus, the long-debated, but constantly delayed Trans-Saharan Railroad was rapidly latched onto, with construction starting from Kenadsa and the nearby city of Colomb-Béchar, heading off into the wastes.

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The plan envisioned that construction would take place over 6 years, at the rate of 1 kilometer of railroad per day, from Colomb-Béchar across nearly 2,000 kilometers of desert to Gao in Mali, then to link up with the existing Dakar-Niger railroad at Bamako. Thirdly, there would be this existing railroad. A total of 3,650 kilometers of railroad, a tremendously expensive endeavor, at some 1.5 million francs per kilometer, for 5.7 billion francs total. Much of the equipment for the railroad was to be purchased in the US, such as cranes, tractors, tows, and locomotives, as well as railroad ties from Portugal. But rails themselves were a significant problem, and many were sourced via cannibalization of existing lines elsewhere, such as one-track rail lines in Southern France! The problems of flash floods posed a long-term danger to the project, as well as once again, the lack of water the rest of the year, and once again thousands of both foreign workers and now North Africans too, as well as Jews.

At the end of 1942, North Africa was liberated in Operation Torch, and although the Provisional Government of the French Republic would use German and Italian internees to complete the rails up to Abadla dam, only 62 kilometers of rail were laid by Vichy and 36 afterward - a twentieth of the distance which would have to be covered to reach even Gao in Mali. The Trans-Saharan Railroad had proved to be a complete failure.

Although the project is dead, there are still ideas for its resurrection: there is the Trans-Sahara Highway which stretches most of the way across the desert, with some unpaved sections, and it is probable that the last unpaved parts, in Niger, will be finished soon. But for now, the incredible expense, horrific conditions, limited infrastructure support, and the problematic economic viability, mean that the railroad will probably just remain on the drawing board.

3 - Phare du Monde

The Interwar saw a romance with the automobile across the world. Modernity, progress, the promise of speed, individualism in the democratic states. From fascist regimes, democracies, or empires across the world, there was a shared appeal of the car. Combine this with the seemingly eternal human ambition to build ever higher, and a good touch of art deco, and you get the Phare du Monde - a gargantuan proposed observation tower and restaurant, which would have been nearly 700 meters high! Intended to be the centerpiece for the 1937 Paris Universal Exposition, the most ambitious element of it - if such a thing can be said after discussing a 700 meter tall tower - was the spiral access road built to wrap around the tower, which visitors would drive up, to a 500 car parking garage at the top! And once there, a 2,000 person restaurant, and a massive beacon on top to compete it all. The sheer length of time that it would take to drive up to the top is stunning—30 revolutions of massive size, and one is talking serious travel times.


An architect's dream is an engineers nightmare, and it is difficult to really see a tower such as the "Lighthouse of the World," as being feasible, even today, much less in the 1930s,and that's before one has to consider who would pay for it and how it could possibly have been built on time for the 1937 exposition, given that it was proposed in 1933. But it certainly shows the ambition and panache of French architects.


4 - Tour Maginot

As clearly impractical and near-insane as the Phare du Monde was, its ambition pales to insignificance next to the mighty proposed Tour Maginot of 1934. 1930s France was a country haunted by memories of the Great War. The French people dreaded another bloody war, and dreamed that through concrete and steel, a future invasion of France could be prevented and lives spared. This made the Maginot Line tremendously popular, and although there were much deeper strategic reasons behind it than just being the great wall of France, it was perceived as a guarantee against the horror of yet another German invasion.

But if the Maginot Line protected France against ground attack, Fortress France had no roof. What was more, the 1920s and 1930s were filled with visions of apocalyptic destruction rained down from the air. The deadly nature of air attack, theorized by air strategists like the Italian Douhet, was envisioned to be so destructive that it would be equivalent to a nuclear war today—when Britain went to war against Germany for example, casualties were predicted to be hundreds of thousands in the first weeks! Urban life, industry, civilization itself, would be razed by the bombs. Something had to be done to defend the skies, and not just the borders of France, and the architect Henri Lossier seemed to have just the solution in 1934: a giant air defense tower. It would incorporate aircraft launching, hangars, and anti-aircraft defenses in a thoroughly massive tower in Paris, which would be 2,400 meters high.

It had a certain logic, as crazy as it might sound. The problem in resisting bombers with fighters in the 1930s was that bombers came in high and fast, and with only sound-ranging systems and observation to detect them. By the time the intruders had been spotted, their course plotted, fighters readied, scrambled, climbed to altitude, and hopefully spotted and prepared to intercept the bombers, they would probably have already dropped their bombs - and that's in the optimal situation, the bombers might escape interception completely. But what if the aircraft were already at the bomber's altitude? Keeping standing air patrols would have been very difficult in the 1930s, in light of the limitations on fuel and range, as well as the cost to keep the aircraft in the air (although in light of the proposal to solve this, it seems to be a pittance....), but Lossier's plan was simple: just bring the airfield to the bombers' height, or close to it.

Along the massive stalk of the tower there would be several conical extensions, serving as airfields and anti-aircraft artillery positions, as well as being armored to protect against bombs. These airfields would have aircraft launching facilities from arch-covered tubes, which would slope downwards, launching aircraft into the air to first lose a small amount of altitude before regaining speed, at already nearly a mile in the air. They would land below at a conventional airfield, and taxi to the tower, at which point they could be raised by freight elevators back up to their launching systems, and regular maintenance performed. In normal operations, a couple dozen aircraft could be accomodated, and several times more this in more crowed situations. Anti-aircraft guns, including large caliber ones, could be mounted to fire out of the ports of the airfield, with again the idea of increasing their height and hence effectiveness.

Of course, such an idea had inherent drawbacks—the main one of course, was cost. In theory, according to the calculations that Lossier performed, a concrete structure could be constructed to reach 6 kilometers high, and a steel reinforced one up to 10 - more than the height of Mt. Everest! Furthermore, the thick concrete walls, 12 meters at the base, would have protected it from any bomb existing during the day. But in practice the sheer cost associated with it would be mind-bloggling, incomprehensible. 10 million tons of material were projected to be used, compared to the Eiffel Tower which merely weighs 10,000 tons - a thousand times more! And all of this would just net a higher launching point for a few score fighters, In the end, it was simply more efficient to invest in better performing interceptor aircraft, and later radar, rather than building such a massive tower.


5 - Corbusier's Paris

Corbusier is an architect who divides many: a visionary of modern architecture and a sculptor of concrete, or a vandal who created a noxious unsightly brutalist style which has destroyed local traditions and architecture the world over? Personally, I fall more on the second side of the argument, so I'm very pleased indeed that Paris didn't get Corbusier's imagined 1925 makeover, the famous "Plan Voisin!"

Financed by the French automobile and aircraft magnate Gabriel Voisin (who would probably have been quite well served in the creation of a city which would be far more geared around automobile traffic), Corbusier's vision was to raze central Paris to the ground on the right bank of the Seine and replace it with massive cruciform concrete and steel skyscrapers. No fewer than 18 of these behemoths, each up to 60 stories tall, would have been built, capable of housing somewhere from 500 to 700,000 people, massively increasing the population density of central Paris from 300 to 1,300 people per acre—in an already notably dense city. However, since the skyscrapers were so tall, the population could be concentrated in them, and they themselves would only take up around 5% of the terrain, much of the rest of it being given over to green spaces. Much of the central city would have been destroyed, although not all buildings would go—the Louvre, Palais royal, and the Place Vendôme would have escaped the axe and been preserved.


This would carry some advantages, according to le Corbusier. The section where this urban revitalization was to be built, le Marais, was somewhat dilapidated and unsanitary, prone to tuberculosis outbreaks, and his new city would have plenty of space for gardens, light, air, in between the massive buildings. It might even be possible to put an airport in central Paris! Transport would be brought to a centralized central transportation exchange, with rationalized transport on different graded levels for automobiles (with dozens of kilometers of highways), pedestrians, and streetcars. A city designed for the automobile, with massive roads and communication axes, which would match Corbusier's vision. But of course, it would also utterly destroy historic Paris, and the problems that we associate with today's cities and Corbusier's designs in particular, with automobile congestion and pollution, dilapidation of massive apartment buildings which lack any spirit of community or neighborhood and which easily degenerate into slums,

Paris is a city which was reborn into the capital of the world under the Second Empire, when a massive program of urban reconstruction and redevelopment, the Haussmannization of Paris, turning a city of narrow streets, crowded quarters, and old buildings into the Paris of today, with its wide boulevards, stately parks, squares, avenues, and elegant 6 story apartments. If there is a city in the world which has been truly transformed, it is Paris. So it is not nearly as unreasonable as it would seem for Le Corbusier to suggest to raze Paris and rebuild it, just as Haussman did 70 years before. But thankfully from my perspective at least, it never would happen: Paris sera toujours Paris, and not in concrete!

A Depiction of What Paris Might Have Looked Like


6 - Ferdinand de Lesseps' Sea-Level Panama Canal

The French diplomat and financier Ferdinand de Lesseps had already built the Suez Canal in Egypt when in 1879 an international conference presided over by him met in Paris and voted in favor of building another canal—this one to pierce the Panama isthmus, largely along the route of the Panama Railroad, and to enable oceanic transport across the very heart of the Americas. Like the Suez Canal, this would be a sea-level canal, but with some assets which might seem to make it more appealing to construct on the face of it—a significantly shorter distance to cross, and if the jungle climate of Panama might be forbidding, the Suez Canal was built in the burning scorching heat of the Sinai Desert. But the problems were far more extensive on the Panama side: unlike the Suez, where the canal was essentially just a ditch through a flat desert, in Panama, there were mountains, and at the lowest point there was still 110 meters high of unstable earth to excavate. Up to 120 million cubic meters of earth would have to be excavated—nearly twice that of Suez. And this could very well have been an underestimate, given that the unstable nature of the earth and constant collapses required for the canal's sides to be continually widened. Rivers would have to be diverted so as to not flow through, such as the Chagres—which wasn't ever solved, and yet the Chagres would flood in massive quantities at times of the year and potentially destroy the canal if not dealt with, and yet the dam project was impractical. The climate was forbidding, with tropical diseases like yellow fever and malaria— these had been brutal reapers of empires and their builders for centuries. The French entered the construction for the canal with foolish, unjustified optimism and excessively low cost and time projections. Engineering parties had been sent even before the 1879 conference and had reported back in favor of the locks canal: they were ignored.

Tidal currents on the South side, ie. the Pacific, are very intense, and this would result in potential major current problems for ships navigating through it, and require a tidal lock - meaning that even a sea-level canal would still require a lock, even if less than a canal with locks. In the present day, the mildly different sea levels of the Atlantic and Pacific would probably be an ecological problem too, given that it would lead to a constant flow through the canal and hence a significant invasive species problem - but this would of course, not have been any real problem for 1880s planners. But environmental problems would prove a terrible obstacle nevertheless - up to 40,000 laborers, mostly afro-Caribbean workers, were assembled - and 22,000 would die, with 5,000 being French citizens.

French workers at work hauling rock.

French workers at work hauling rock.

The miracle about the French Panama Canal was that it was approved and went through, when the nature of the engineering challenges meant that it should have been cancelled or modified from the beginning. Other projects like the Tour Maginot or the Phare du Monde look deeply impractical—but they were never approved, never went forward with construction. In Lessep's sea level Panama Canal, the halo surrounding Lessep after his successful completion of Suez, uncritical acceptance, and bribes to important politicians to support it, helped lead to a costly - and murderous, boondoggle.

But thankfully it wasn't completely worthless—the French had moved scores of millions of tons of material, some 59 million tons, dredged supporting canals, carried out surveys, and left behind large amounts of machinery. While the canal for the French was a disaster, one which cost the Panama canal company bankruptcy, ruined many French investors with the 40 million dollars that the Americans bought it for hardly covering the cost, and led to a major political scandal about the bribes associated with it in France, it did lay the groundwork for the ultimate successful completion of the Panama Canal. And there have been proposals for a sealevel canal since, mostly in Nicaragua - but these would probably require the use of nuclear bombs.

The maximalist plan of territory to be flooded - note the comparison to Lake Geneva in the bottom right corner.

The maximalist plan of territory to be flooded - note the comparison to Lake Geneva in the bottom right corner.

7 - Flooding the Sahara

"The Sahara is the cancer eating away at Africa. We can't cure it; therefor, we must drown it." — François Elle Roudaire.

The 19th century was full of predictions about the ability of man to change the environment, for better or worse; The rain was thought to be brought by the plow on the American plaines, and in Russia the felling of trees on the steppes of Southern Russia and in Ukraine led to fears that drought and drying up of the land would inevitably follow.

French North Africa responded to a similar logic: it was believed that the fertile soils, once the granary of Rome, were in the past much more green and verdant they were by the time the French colonized the region after 1830. French researchers thought that the Arab invasion, bringing herding cultures and a prevalence of goats and camels, was responsible for the destruction of forests and the advance of deserts. The desert was the great enemy of the French, the endless expanses of sand haunted by fierce warrior peoples, and many a French colonial planner must have dreamed of following in the footsteps of Rome and turning the sandy wastes into lush fields—but the question was how?

This is where François Elle Roudaire enters the picture. A French army surveyor in southern Algeria, he measured the chotts (salt lakes) of southern Algeria and Tunisia, and believed that many of them lay below sea level—up to 40 meters below! This sparked dreams that it could have been the ancient Lake Triton, written about by the Greeks as a vast freshwater lake in North Africa. If one wanted to put paid to the desert expanse of the Sahara, all that would be necessary would be to build a canal for the Ocean to enter to drown it - from the Gulf of Gabes to the Chott el Fejej. This would provide water transport, and would also alter the climate through additional coastline and a large expanse of water which would evaporate and produce additional humidity—articles at the time such as in the New York Times reported massive figures of water evaporation, which would presumably make Tunisia and Algeria much wetter. Not only Roudaire, but also the famous French canal builder Ferdinand de Lesseps, constructor of the Suez canal, through their backing behind the project in the 1870s.

A map of those regions of Southern Tunisia  with those parts which are actually below sea level.

A map of those regions of Southern Tunisia with those parts which are actually below sea level.

Unfortunately, or fortunately given that such radical environmental modifications would probably have unintended consequences, later surveys showed that only a much smaller proportion of the region was actually below sea level—and this the areas which were the closest to the sea, the Chott el-Djerid. Lopping off 6 to 8000 square kilometers from the lake and requiring a 240 kilometer long canal cut much of the elan from the project, tremendously expensive for little benefit. Roudaire died an early death at just 48, and his plan was never adopted. It did however, inspire Jules Verne in his last book, L'Invasion de la mer (The Invasion of the Sea)- but it will probably always remain within the pages of fiction, despite occasional proposals to resucitate the project.


Other ideas have emerged in the North African sands as well, such as the Qattara Depression in Egypt, where it was hoped that the usage of 213 1.5 megaton nuclear bombs could create a channel that would generate massive amounts of hydro-electric power from water falling up to 60 meters from the Mediterranean, as well as providing valuable chemical products from the evaporation. But until someone gets permission to utilize enough nuclear firepower to destroy a major nation, this will probably not go ahead.


Robert Clarke from UK on June 24, 2021:

Fascinating article and images. I used to hate brutalist architecture but I later developed an interest in Le Corbusier's work. Still glad some of those monolithic masterplans never saw the light of day though. But I do like some of his buildings like the one in Marseille.

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