I received a tremendous amount of interest when I tweeted out about the May 2 1945 Flooding of the Underground - that when I was in High School, we were taught that it was Adolf Hitler who ordered this done.
But there is controversy if it was Sabotage by the invading Russians, or an order from the Fuhrer, or just an accident in a time of war.
The number of deaths due to drowning is also up for argument. But what is known is
There were substantial Berlin U-Bahn sections flooded in May 1945. A prominent cause was an intentional sabotage by the detonation of explosives in the Berlin Nord-Süd Tunnel beneath the Landwehr Canal on the morning of 2 May 1945. By the end of the war, several sections were flooded:
Flooded North–South Tunnel 1946
Rosenthaler Platz – Jannowitzbrücke
Uhlandstraße – Wittenbergplatz
Wedding – Gardepionierplatz
Mehringdamm – Kreuzberg
Alexanderplatz – Potsdamer Platz
Alexanderplatz – Frankfurter Allee
There is controversy about the cause of the flooding, with some attributing it to a Nazi order, but insufficient evidence of this has been found and it has not been possible to say with certainty who carried out the sabotage and on whose orders. Similarly there has been controversy about how many people had lost their lives as a consequence. It is most likely that some the bodies found later in the tunnel were wounded soldiers who had been dead before the tunnel flooding, since the S-Bahn tunnel station under the Friedrichstrasse station was used in the last days of the war as an emergency military hospital, with trains used as hospital rooms. It seems clear that some did die in the flooding, but the discrepancy between the number of bodies recovered and the number anticipated has given rise to conspiracy theories. Current research suggests probably less than 200 deaths were caused by the flooding
Waters discharged into one third of Berlin's Underground flooding 63 km of tunnels with 25 further stations.
Another but smaller leak in the tunnel ceiling under the Spree River was either caused by German forces exploding the Ebertsbrücke street bridge crossing at the river at the same section, where the tunnel passes underneath, or some months later, after the end of fighting, by the Soviet army who created the hole in the process of clearing the Spree river of large concrete obstacles created by the bridge explosion.