He worked in many styles, but most often in a simplified neo-Romanesque, and designed important public buildings both in the Weimar Republic and under the Third Reich, including major bridges for the new autobahns.

In February 1935 he gave a speech inveighing against architecture which made "the act of representing an end in itself" rather than form coinciding with function in which he called Albert Speer's New Reich Chancellery "patently inadequate".

[8] His younger brother, Karl Bonatz, was also an architect and was chief planner of (West) Berlin succeeding Hans Scharoun.

The Stuttgart station, which was influential, has been seen as a transformation of historicism: the building itself was modern, the historical decor purely stylistic accents.

[11] Like Fischer, Heinrich Tessenow and German Bestelmeyer, he appealed to the Nazis because many of his works bore a clear relationship to traditional styles; Paul Schultze-Naumburg expressed the völkisch school's approval of the Stuttgart station as "a modern technical building in the best sense of the word.

The brick edifice was constructed in 1924–30 and was mostly designed by the Bulgarian architect Georgi Ovcharov, who worked the project out at Bonatz's office in Stuttgart.