The most imposing feature of the tidal basins (“ bassins à flot ”) in the Bordeaux dockland area is the submarine base built by the Germa...

La base sous-marine: the ghostly WW2 u-boat pen

The most imposing feature of the tidal basins (“bassins à flot”) in the Bordeaux dockland area is the submarine base built by the Germans during the Second World War, one of six constructed in France.

Early in the conflict, Bordeaux had been chosen by the Italians to station their “Betasom” fleet of submarines (the Greek prefix “Beta” in reference to the “B” of Bordeaux, “som” being short for sommergibili, or submarine in Italian). From the base, Italian submarines participated in the 1940-1943 Battle of the Atlantic as part of the anti-shipping campaign against the Allies. The Germans soon noted the strategic interest of the city’s location, far from the inland front lines and ideally positioned for operations in the Atlantic Ocean.

In the summer of 1941, the decision was taken by one Admiral Dönitz to build a protective bunker in Bordeaux, and construction work began in September of that year. By October 1942 the first German u-boats were stationed there and the base went on to become the home of supply boats, mine-layers, torpedo transports and, above all, the 42-strong 12th Flotilla of very long-range boats. Some of the longest voyages of the war set out from Bordeaux, including a 225-day patrol that was completed in October 1943. After the Italian capitulation in September 1943, five of their submarines were also taken over by the Germans.

The 12th Flotilla was disbanded on 25 August 1944 ahead of the imminent arrival of the Allied forces, who went on to seize the base. Three surviving submarines succeeded in escaping to Germany and Norway and were transferred to other fleets. At the base itself, just two unseaworthy submarines remained. Both were scuttled.

The scale of the structure is mind-boggling. The bunker, which covers a total area of 43,000 square metres, is 245 metres long, 162 metres wide, 19 metres high and much of its roof is a near-indestructible 9.20 metres thick. 600,000 cubic metres of concrete were used to build it.

There are 11 berths in all. Pens 1 to 4 are wet docks, each of which is 20 metres wide and 106 metres long. They could each house two u-boats. Pens 5 to 11 are 14-metre-wide dry dock cales, ranging from 96 to 104 metres in length. Each could house one submarine, the water being removed whenever necessary through the use of powerful pumps.

Construction work on the bunker was only complete in mid 1944. It is estimated that up to 6,000 workers, mainly Spanish and Portuguese prisoners of war, worked relentlessly day and night in merciless conditions. While a popular urban myth suggests that some fell into the depths of the building's foundations where they perished as the concrete slowly set around them (today most authorities do not believe that to be factually correct), it is true that many of the construction workers died in accidents, of exhaustion, or drowned. A solemn memorial has been erected in tribute to those who took part in the construction, and particularly to those who lost their lives.

Today the berths are hauntingly empty shells, occasionally used by amateur yachtsmen when working on their boats. Sections of the building are used for cultural events (drama, exhibitions and concerts) but it seems that the place will never shake off the cumbersome weight of its war-time legacy.

It will however be interesting to monitor the area in the coming years as the city of Bordeaux seeks to re-develop the docklands into an attractive environment to which people will be drawn to work, rest and play. The first landmark project, the highly-awaited Cité du Vin, thus saw the day in 2016.

Much has been written about the u-boat base, but the following are of particular interest:

> Further photos, including some taken inside the base itself, can be viewed at
> Meanwhile, some incredible historical shots, including one of the base mid-construction and another of the ceremonial inauguration in 1943, can be seen here:
> Cet article est également disponible en français !


  1. A fascinating topic. What is interesting is that these are still standing despite their more than dubious past, but as they were 'indestructible' perhaps that should not be a surprise!

    It is also interesting to note that as structures they influenced a whole generation of brutalist architects in the UK in the 1950s and 60s, although this influence - although obvious - was never directly mentioned!

  2. In a sense, the bunkers are possibly a unique "Invisible Bordeaux" subject: given their size, they couldn't be any more "there", physically, yet their history means that most people probably see them without really seeing them.

    I agree that it'll be interesting to see what becomes of the area after redevelopment.

  3. I think the area will be totally revitalised with the arrival of the "CCTV" (more of which a little further down the line) and the grand plans for swish residences. But how a WW2 u-boat bunker (which cannot be separated from its history) fits into that picture remains a mystery. To be continued!

  4. Hadn't heard of this place before, but am always grimly impressed with the longevity of many of the heavy concrete structures that remain more or less intact today that the Germans built back during the war. Even structures from WWI that still exist. They were prolific in their construction of bunkers and blockhouses, strictly functional in their goal of sowing death and destruction. What an incredible amount of wasted energy and blighted landscapes. Great post...

  5. There'll be more bunkers in an upcoming post, but they'll be Atlantic Wall structures that haven't fared quite so well... Watch this space!... :-)

  6. Look foreword to seeing more Tim, I will be visiting them next August. Hopefully the La Rochelle pens aswell, providing I can get in them! Is it possible to get inside at Bordeaux, and maybe on the roof?

  7. Not sure about the roof but you can definitely get inside the structure by visiting the temporary exhibitions which are held there, 2pm-7pm every Tuesday to Sunday during the summer months. Check out this page for further information and an idea of what to expect:

  8. Cheers for the link Tim, some good images on there.

  9. That was such a good idea to write on the history of that building ;) See you maybe in Brdx, I'm also ridding a bike in this city.

  10. Please have a look here ! >>
    My forum talks about many unknown locations during world war 2 !
    That is Urban Archeology !!

    Best regards


    1. Thanks Erwan, it looks like a fantastic resource and I will be signing up!

  11. I have just visited these u boat pens in mid October 2013. The whole area is about to be redeveloped and billboards with areil artists diagrams are already up in the area. They depict a massive rooftop garden with trees!. A welcome change as the buildings are as ugly as they are impressive in size. My father was in the navy during the Atlantic war. It gave me the creeps just looking at the place.

    1. It is a sinister sight but, absolutely, over the coming years the place will change radically. The first swish new residences are already going up...

  12. Last year I visited this place. Underwater Base is one of five bases built on the Atlantic coast to house fleets of submarines U-boats during the Second World War. Its construction by the German occupation forces began in 1941 and ended in 1943. This gigantic bunker is organized into eleven interconnected by an internal street alveoli. The set covers an area of 43,000 m2. thanks for sharing! ~ Ketty H.

  13. I went to the Georges Rousse exhibition there the other weekend, there's a weird boat filled with old teddies anchored just away from the building, close enough to see but not really understand. Do you know anything about his!? Very creepy.

  14. Why would it have been built with Spanish and Portuguese prisoners of war? Neither of those countries took part in World War Two, and if they had it would have been on the German side.

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