Berlin is filled with non-places, strange spots where history feels like a force field keeping people away. One such place is a patch of grass, empty except for some randomly-placed trees, adjacent to the modern chancellery. Few who pass this way know it was once the site of the Kroll opera house, demolished in 1951. From 1933, after the mysterious fire in the Reichstag opposite, the opera house became Germany’s provisional seat of parliament. It was here that German MPs voted out democracy for fascism, and where Hitler justified his invasion of Poland in 1939, triggering the second World War....