Everything You Never Knew You Wanted to Know About Berlin


Did you know that an old street-tram tunnel under the River Spree still connects Treptower Park with the Stralau Penninsula? However, do not plan any excursions yet: the tunnel has been flooded for some 70 years. Well, not all of it, though…

Straube-Plan of the future Treptower Park are with the Spreetunnel under construction (1896).

Straube-Plan of the future Treptower Park are with the Spreetunnel under construction (1896).

The tunnel, constructed by a large Berlin engineering company, AEG, to prove the viability of their idea of building an underground railway network embedded in the famously treacherous Berlin soil (the centre of Germany’s capital is basically floating on top of endless masses of mud, sand and groundwater), became the first public railway tunnel in Germany.

Gesellschaft für den Bau von Untergrundbahnen GmbH, established by AEG, wished to convince the city elders that it would be possible to have an underground railway line between the north and the south of the city – an idea that made many people visibly uneasy. However, not as uneasy as the competing project by Siemens & Halske to install a Hochbahn, an elevated railway, right through the main streets of Berlin.

The southern end of the Spreetunnel Stralau in Treptower Park (1899).

The southern end of the Spreetunnel Stralau in Treptower Park (1899).

The Spreetunnel Treptow-Stralau (not to be confused with the U-Bahn Spreetunnel built later under the Spree a couple of kilometres further north) was 454 m long (582 m counting the ramps) and ran twelve metres under the river bed. Its approximately four-metre wide interior housed a single track used by trams travelling back and forth along the line.

The line came to be known as Knüppelbahn: Knüppel, a wooden baton, was passed between the drivers to make sure that only a single vehicle, one whose driver had the said Knüppel with him, enters the tunnel before another one does the same at the other end. An almost fool-proof system as the future was to show.

The journey along the tunnel and under the Spree lasted almost exactly two minutes.

The tram line, by the way, was not AEG’s idea – it was installed upon an explicit wish of the Stralau parish on whose land the tunnel was partly to be built and without whose consent the project could not have been carried out.

Inside the tunnel.

Inside the tunnel.

In February 1932 the service had to be terminated: cracks appeared in the tunnel walls and the number of passengers ceased to justify the line’s existence. The cracks were no surprise: the tunnel, built using the shield tunnelling technique typical in coal-mining back then, was not exactly perfect. The method, which had been criticised by Siemens & Halske and which delayed the construction by three years (initially, the opening of the tunnel was planned for the 1896 Great Industrial Exposition in Treptow) had some disastrous side-effects: for instance, sand kept sliding into the freshly excavated tunnel so that far more of it had to be removed from the site than had actually been dug to build the tunnel. The second thing was even more worrying: a test wall built on top of the area under which the tunnel was constructed developed deep cracks and eventually collapsed.

Even though the craftsmanship of the tunnel’s designers and builders was superb, the choice of the method proved to be far from perfect for the conditions in which it was used, read: under a large river.

Still, the Spreetunnel re-opened once more for the Berlin Olympics of 1936. It was renovated on the behest of the Nazi authorities and served as a pedestrian tunnel for numerous guests of the Olympics. It did not fail to impress. A couple of years later, however, in 1944, its northern end had to be converted into an air-raid shelter for the people of Stralau (the northern end was less likely to fill up with water in the case of the tunnel’s being hit by a bomb).

Four years later its fate was sealed: since its restoration would have meant immense costs and made no sense anyway since the city had bigger problems to deal with, the tunnel was completely flooded and sealed. The exit in Treptower Park, next to “Haus Zenner”, was removed along with a section of the tunnel in 1968.

The northern end of the tunnel in Stralau - today the entrance to the tunnel is buried under the green mid-strip in Tunnelstraße. (image through

The northern end of the tunnel in Stralau – today the entrance to the tunnel is buried under the green mid-strip in Tunnelstraße. (image through

In December 1996 the ghost-tunnel had to be re-visited again. Berlin’s fire brigade pumped out the water filling the Spreetunnel Stralau again to allow the inspection of its condition before the big construction projects in Stralau began. The old air-raid shelter was practically intact: the benches, the old first-aid kits, even the crockery were as if frozen in time inside it.

Locked and flooded again, the tunnel still extends under the river. What remains of it on the surface are two place names: Tunnelstraße in Stralau and Platz am Spreetunnel in the Treptower Park. The extra side-entrance, which until recently could be found on the site in Treptow and was filled with water, too (only accessible to divers, if anyone), was removed as well.

The story of the Spreetunnel between Treptow and Stralau is, along with many other fascinating Berlin facts, included in “Notmsparker’s Berlin Companion” available at


  1. Gary Costello
    Dec 16, 2016

    You have again suceeded in making a grown man get all excited about Christmas! Reading your posts over the last four days, has made me look towards the Christmas tree and the one present who’s content I already know. It has been a long time since I looked forward to opening a present at Christmas, I have even started counting the days!
    So keep up the great work, I will continue to look forward to your posts. Oh, how many days is it till Christmas?

    • notmsparker
      Dec 16, 2016

      Glad to make you look forward to that present, Gary. Only a week to go.

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