Albert Speer became Hitler’s preferred architect for Berlin through the Second World War because of his grand scheme for the city. If all of his highly expensive plans had been carried out the city, he hypothesized, would be more splendid than Paris. More splendid than Vienna.
This was an idea highly attractive to Hitler, who wanted the Third Reich to be better than all of Europe. Speer was chosen out of numerous architects because he never told Hitler his ideas were too grand either because of physics or budget constraints.
Almost none of Speer’s building designs were actually created, but I found some pictures that depict just how large a scale Speer imagined for Berlin.
You really get a sense of the neo-Roman elements of Speer’s plans from the lower image.