The Life, Death, and Resurrection of Germany’s Massive U-Boat Bunkers

At the end of June, my husband Andy and I visited the French city of Bordeaux for the first time. I often plan a full agenda when we travel but this year we left much of our daily itinerary to chance and whimsy. A week before we boarded a train out of Paris, I’d read about a digitized light show staged inside a former Nazi submarine base. During World War II, the Germans installed 5 fortified U-boat pens along France’s western coastline. All of these colossal structures are still standing and a few have been transformed into cultural spaces. Such is the case in Bordeaux. Home to Les Bassins des Lumières, the source of one of the Allied Forces’ worst nightmares now harbors a sound and light show of spectacular beauty.

To fully appreciate the venue where this visual and auditory extravaganza takes place, it helps to know a bit about the former submarine bunker that houses it. In this post, I present a brief history of Germany’s once-formidable U-boat fleet and the fortified pens that serviced them. It’s hard to convey the scale and solidity of these monstrous structures. As you read, keep in mind that despite British and American bombers dropping thousands of tons of explosives upon them durng World War II, all 5 pens remained virtually unharmed.

Bassins des Lumières
A digital exhibit of artistic and architectural treasures of Venice at the Bassins des Lumières.

A Breakneck Invasion and Iron Fist Rule

After toppling the Netherlands and Belgium in a matter of weeks, then driving British troops from the European mainland, it took German forces only 20 more days to capture Paris and convince France to sign an armistice on June 25, 1940. As part of the agreement, France’s territory was divided into two zones. The northern half of the country, as well as the Atlantic coast, was controlled by the Germans in the Occupied Zone. The southern half, initially referred to as the Free Zone, was governed by a puppet regime. In 1942, it too fell under the administration of the German army.

Occupied Zones of France
Map of Occupied Zones of France

Two months after France’s capitulation, the Germans established a naval base in Bordeaux. Hitler was determined to cripple Britain by any means possible. In order to survive, the island required more than a million tons of imported material per week. Admiral Karl Dönitz, commander-in-chief of Germany’s submarine (unterseeboot or U-boat) fleet, believed that disrupting these shipments was key to winning the war. As thousands of laborers worked to construct Nazi naval bases along France’s Atlantic coast, Mussolini stationed 32 Italian submarines (nearly half of his fleet) in the newly captured port of Bordeaux. Camouflage nets were installed above the quays to conceal the subs from Allied aircraft.

Italian submarine
An Italian submarine lies beneath a camouflage net in Bordeaux.

Germany’s Colossal U-Boat Pens

Dönitz knew that his naval bases would be prime targets for the Royal Air Force. As a result, Germany began constructing massive concrete pens to protect its U-boats from British air strikes during refueling and repair operations. In September of 1941, work began on the bunker in Bordeaux. The colossal structure required 60,000 cubic meters of reinforced concrete and took 6,500 laborers, often working around the clock, 19 months to complete. More than a third of the workers were Spanish republican prisoners. The remainder of the force was comprised of men from Germany’s occupied territories—some of them voluntary, others not—and German technicians.

Workers at the Bordeaux base
Construction workers at the Bordeaux base, 1943. Photo © SZ Photo / Scherl / Bridgeman Images.

When completed, the Bordeaux pen consisted of 11 submarine docks (7 of which could be used as dry docks to conduct repairs), 11 technical workshops, and a 4-story power station. To withstand an airborn attack, stockpiles of fuel and torpedos were stored remotely, connected to the bunker via an underground pipeline and railway track, respectively.

German officers at U-boat bunker
German officers pose in front of Bordeaux’s U-boat pen.

The Costliest Naval Battle in History

In January 1943, Germany’s 12th U-Boat Flotilla began stationing its submarines in the new bunker. The Germans erected a vast anti-aircraft defense and bomb shelter system to protect their lethal fleet from Allied strikes. Over the remaining months of the war, the bunker serviced 43 U-boats that conducted attack missions throughout the Atlantic—patrolling as far as the Americas.

U-boat returning tp its pen
German U-Boat returning to its pen in Bordeaux.

On May 17, 1943, the base was the primary target of an American air strike that dropped 198 bombs on Bordeaux. The attack caused considerable damage to the harbor and killed close to 200 civilians. However, while the U-boat bunker was hit, it suffered only superficial damage thanks to a 9-meter thick concrete roof, reinforced with corrugated sheets and topped by a 32-ton trellis of concrete girders.

Bordeaux after American airstrike
Bordeaux after the American airstrike of May 1943. Photo © LAPI/Roger-Viollet

It would take another 15 months until German troops finally abandoned the bunker on August 26, 1944. Two days later, Bordeaux was liberated without a fight. During the war, the Italian fleet stationed in Bordeaux sank 109 ships. The German fleet sank 104. Ultimately, however, these flotillas also suffered heavy casualties. By the end of the war, 36 of the deadly U-boats and 15 Italian subs had been lost during operations.

Liberation of Bordeaux 1944
People surround a French soldier in the streets of Bordeaux, August 28, 1944.

A Colossal Waste

Over the course of the war, Germany built close to 1200 U-boats. The 5 montrous bunkers that still blemish France’s western coast represent Germany’s most impressive engineering feat executed in occupied territory. Ultimately, the German blockade failed but the losses on both sides of the sea battle are staggering. German subs managed to sink 3,500 merchant ships and 175 warships in the Atlantic. In return, the Allies took out 780 U-boats—519 were sunk by British, Canadian, or other allied forces, 175 were destroyed by American forces, 13 were destroyed by the Soviets, and 73 were scuttled by their crews before the end of the war. Of the 38,000 men who served in U-boats during the war, only 8,000 survived.

U-boat sunk by airstrike
U-boat battered by airstrike

During the years of reconstruction that followed World War II, Germany’s U-boat pens proved to be so well-fortified that tearing them down was cost-prohibitive. The French Navy assumed control of the bunkers and continues to uses portions of the docks and workshops. Much of the space, however, has been repurposed over the years, housing a variety of enterprises, from metalworking shops to museums to retail. Even so, the space within these edifices is so enormous that many of the docks still lie empty and in disrepair.

Les Bassins des Lumières

In 2017, the city of Bordeaux put out a request for proposals that would utilize 4 of its 11 U-boat basins for cultural enrichment. Three companies submitted plans and in September 2018, the contract was awarded to Culturespaces. Founded in 1990, Culturespaces is a private organization specializing in the management of historic monuments and museums, and the creation of art centers. They have become a world leader in the production of immersive digital art exhibitions. You may be familiar with their initial digital exhibit space in Paris, Atelier des Lumières.

It was into this mind-boggling setting that Andy and I stepped last June. I’ve placed the details of the bunker’s transformation and our memorable visit in a different post. For now, I can only say that the juxtaposition of evil and exhilaration that reverberated through my mind that day left me a bit shaken. I was at once in awe of humankind’s limitless capacity for invention, while deeply disturbed by the evil actors of our species that repeatedly threaten human survival. You’ll find more on that story here.

U-boat pen under construction
Bordeaux’s U-boat pen under construction, 1942.

Other Resources

About Carol A. Seidl

Serial software entrepreneur, writer, translator, and mother of 3. Avid follower of French media, culture, history, and language. Lover of books, travel, history, art, cooking, fitness, and nature. Cultivating connections with francophiles and francophones.


  1. Thanks for putting all this information together. I’ll look forward to the future post on modern conversion of U-boot pens. I had never heard about that before.

    The German use of slave labor for military purposes was widespread and often turned out to be foolish. The V-2 rockets were largely made by slaves, who took every opportunity to sabotage the mechanisms, so that quite a few rockets failed in flight. Slaves, of course, had no interest in supporting the Nazi war effort. Unfortunately the type of work involved in building the U-boot pens probably didn’t allow much opportunity for sabotage.

    It’s sad that the US air raid killed so many people in Bordeaux. In a way, the Nazis were using the local civilians as human shields. Bombing at that time was horribly inaccurate. Modern cruise missiles would have made short work of the pens, probably with negligible collateral damage.

    I’ve been in a World War II U-boot. They had one permanently docked in Bremen harbor and open to the public when I was there in 1984. It was horribly cramped and claustrophobic, and sailing in it in wartime must have been terrifying. The German people I was staying with felt the same way. They hadn’t known much about that detail of the war. It’s sickening to think how the megalomania and obsessions of just a few men unleashed so much horror that engulfed millions.

    • Interesting but not surprising to hear that the Nazi prisoners sabotaged rockets. You’re right that its a bit harder to sabotage poured concrete.

      I’ve also been in a U-boat. There is one in the Chicago Museum of Science and Industry. I’d had the courage to step in when I was in my 20s but on a return trip with my kids, my claustrophobia got the best of me and I waited outside while they went in with Andy.

      Have you listened to or read Malcolm Gladwell’s book The Bomber Mafia? He goes into U.S. efforts to develop “precision bombing” and the overly-hyped propaganda surrounding their advancements.

      “Sickening” is right! And sadly, there seems to be no end to humankind’s steady stream of narcissistic sociopaths and the symbiotic devotees that propel them into positions of power.

      • I haven’t read Gladwell, but Beevor’s The Second World War goes into the considerable detail about the different schools of thought about bombing. Unfortunately, given the technology of the time, real precision simply wasn’t possible. We should be grateful to live in a time when the omnipresence of electronics allows us to be more fastidious about how we defend ourselves.

        • I guess I’m glad that we can do a better job destroying another country’s infrastructure without killing its citizens but dang, all the resources we’ve put into toppling our enemies is a sad loss. I’d like to think we’re evolving to be better caretakers of our species and the planet but I sometimes I have serious doubts.

  2. Fascinating. You really do good research, chère amie. I do know quite a bit about WWII but I didn’t know about Bordeaux’s U-Boat base. The number of U-boats you mention is also striking. If I’m not mistaken France only has 12 submarines left. With nuclear capacity of course, but still, sounds so little…
    I take it the “lumières” show was good?

  3. Just as I was reaching the close of your post, I had the same thought: there you were in the midst of these monuments to horror, which have been repurposed as cultural draws.

    One can only hope that eventually, humans’ capacity for creativity and beauty will outnumber such seemingly indestructible reminders of inhumanity.

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