Which punishment was the Nazi Albert Speer sentenced to during the 1946 Nuremberg Trials?

Explanation

Albert Speer (1905-1981) was a German politician and Adolf Hitler's personal architect. He was behind e.g. the Reich Chancellery in Berlin (1938) but also drew up plans on Hitler's orders for Welthauptstadt Germania, a complete rebuild of Berlin, to take place after the war. He was Minister of Armaments and War Production 1942-1945. During the 1946 Nuremberg Trials he was sentenced to 20 years' prison for his role in Germany's Nazi regime.