A column about curious stories from the world of science and technology. Today—a story about water that was pumped out for months so it wouldn’t interfere with construction, then let back in again—on the architect’s own decision. The trigger for this deep dive was a random evening film—Joel Schumacher’s 2004 The Phantom of the Opera, the screen version of Lloyd Webber’s musical, in which a masked Gerard Butler rows Emmy Rossum across an underground lake amid drifting candles. The scene has migrated from adaptation to adaptation since 1925, and every viewer ends up asking the same question: beneath the real Palais Garnier in Paris—that very building where all this happens—is there really water? The answer is yes. But what lies there is more interesting than any candlelit boat, because it is the solution to a purely engineering problem from 1862. And it still works.
Let’s begin with fate’s classic prank. In May 1861, Charles Garnier won the imperial competition for the new Paris Academy of Music—an opera house Napoleon III had commissioned as part of Baron Haussmann’s redevelopment of the city. The scale is impressive even now: around one hundred and seventy designs were submitted, and the winner was thirty-five-year-old Charles Garnier—not a star architect of the capital, but a young man with the 1848 Prix de Rome and a couple of modest churches behind him. The site for the palace was chosen personally by Baron Haussmann—a vacant lot at the intersection of the new boulevards, where the prefect was deliberately shifting the center of city life.
The excavation was dug quickly: on August 27, 1861, crews began the earthworks, and by New Year the four-month dig was complete. And then the story’s main culprit entered the picture: water. Not a “leak,” not a “crack in a joint”—beneath the site lay a full-fledged groundwater table, fed by the proximity of the Seine and the memory of old marsh channels. In February 1862, wells were drilled on the site; in March, a battery of eight steam pumps began operating around the clock. The ground gave up water as fast as the pumps removed it: construction had run into a problem that neither money nor frantic effort could solve.
In the spring of 1862, Garnier made a decision that still turns up in construction textbooks: don’t fight the water—give it a permanent legal home. On June 20, 1862, a contract was signed for a reservoir that would occupy part of the excavation. On July 21, the first stone of the palace itself was laid—and beneath it, a structure designed for eternal coexistence with the aquifer was already taking shape. By autumn, the pumps were removed as no longer needed: the water had been given legal housing. The opera’s opening, delayed by war, the siege of Paris, and the Commune, would not take place until January 1875—but the engineering move had been made thirteen years earlier, and forty-eight years before the novel that would make it famous.
Now, what exactly did Garnier design? Because this is the best part of the story. The reservoir is not a cave and not a force of nature, but a rigorously measured masonry tank beneath the stage and its rear: more than 1800 square meters, fifteen meters below stage level, brick piers and vaulting. Its operating logic is beautiful in its simplicity. Groundwater pushes upward against the foundations—a classic Archimedean force trying to pop the basements out like a cork from a bottle. The standard countermeasure is to make the foundations impossibly heavy, meaning pouring in concrete worth a fortune. Garnier did something else and used water itself as a building material: the filled reservoir equalizes the pressure—water outside and water inside stop forcing their way through the masonry—while the mass of the water works as ballast, just as a ship’s keel does: it lowers the palace’s center of gravity and stabilizes it on loose ground. Historian Jean-Claude Yon, author of a book about 19th-century Parisian theaters, assesses the result without qualification: holding a building of such weight on a boggy foundation was a real feat.
The reservoir had a dual purpose from the very beginning. First, that equalization of pressure and ballast. Second—a firefighting reserve: for a 19th-century building whose stage was lit by candles and gas jets, having a supply of water close at hand was an obvious idea. Hence the third, modern item on the operations list: the Opera’s fire brigade uses the reservoir as a training ground—exercises in dark water, in an enclosed space where visibility is zero and sound behaves as it does in a well.
Over one hundred and sixty years, the reservoir has never stood empty for longer than scheduled maintenance required. The most notable intervention came in 2018: the water was drained for a major cleaning—to inspect the masonry and give photographer Christophe Pélée the chance to shoot the structure dry. The images became famous: for the first time, one could see what the water usually hides—severe columns, bracing arches, neat brickwork. No remnants of a boat, no skulls. Just architecture—exactly the architecture specified in 1862.
So where did the Styx spring from beneath a foundation calculated down to the centimeter? Gaston Leroux, born in 1868, grew up in a city already buzzing with rumors: beneath the new opera house lay water and underground passages where “you could disappear.” Adult Leroux became a court reporter—a trade that teaches one thing: don’t make up details. By the 1900s he had left newspapers for novels, and in 1910 he gathered his reporting skills into The Phantom of the Opera. He had material to work with: he knew the backstage corridors, had acquaintances among the building staff, and knew how to write so that fiction kept step with the chronicle.
Leroux carried out his most devious operation in the prologue. He assures the reader that the phantom exists, that the author personally conducted an investigation, and that while the basements were being prepared for the laying of phonograph recordings, a corpse was supposedly discovered and identified as Erik’s body. Fiction presented in the format of a documentary report. A reader in 1910 could not verify it, and the legend immediately went off in two directions: into musicals and cinema—and into the endless question from visitors, “is there really a lake here?”
The beauty of it is that Leroux invented neither the water nor the shore. He raised an engineering reality onto a literary pedestal and enlarged it: instead of a reservoir, “a lake whose leaden waters vanish into the darkness”; instead of seepage flows, a cell with an organ, a mirror-portal, and a boat. Historian Yon breaks down the trick neatly: the real allure is not in the water itself, but in the idea of sealed depths beneath the stage—a long-forgotten myth of descent into the underworld. Orpheus, walking after Eurydice through the underground river, received a Paris address in Leroux’s retelling. And the ominous scene of the falling chandelier barely required any imagination at all: on May 20, 1896, the counterweight of the great chandelier came loose from its fastening and killed a worker. The novel turned the accident into a theatrical catastrophe before a packed house—but the seed of fact was exactly this: part of the chandelier fell, and a person died.
The water in the reservoir is genuinely alive. Fish appeared there on their own, and this is no legend: according to Le Point, carp inhabit the submerged lower levels, while a Telegraph report from Garnier’s basements describes a large white catfish that the Opera staff, in an act of workplace stewardship, feed now and then—it can occasionally be spotted by the grate. As befits an urban marvel, the site is closed to casual visitors. But not to cameras: Google Arts and Culture has a Street View panorama where you can travel around the reservoir’s inner perimeter without a wetsuit or a pass.
And one final plotline that Leroux retrospectively turned into prophecy. In 1907—three years before the novel appeared—the French branch of the Gramophone company sealed twenty-four records featuring the voices of the era’s finest opera singers into two lead urns and bricked them into Garnier’s underground levels on one condition: they were to be opened a hundred years later. The project was both an advertisement for sound recording and a test of the technology: would sound survive a century? The deadline came in 2007–2008: the urns were opened, the records retrieved, digitized, and released as the compilation Les Urnes de l’Opéra—“The Opera Urns.” Jean-Claude Yon put it beautifully: the Opera’s true ghosts are those voices, which slept for a century in the basements, in the half-light of its imaginary lake.
That, really, is the whole recipe. Reality does the work, and legend paints over it—without touching the layer beneath. Engineering-wise: the 1862 reservoir still bears both the pressure and the weight of the palace. Biologically: fish go on living perfectly well in permanent darkness. In folklore: the story of the lake survived war, film, and musical theater—and still sells tickets—for a theater that has nothing left to prove. None of it would have happened if, in 1862, they had simply ordered more powerful drainage. So if The Phantom of the Opera turns up in your evening again, remember: beneath the candlelit boat on screen, engineers will see a concrete water reservoir with strict geometry and a carp inside. The phantom never lived there for a single day. But the pressure—it still holds.