The Einstein Tower by Erich Mendelsohn. It categorized as "expressionist architecture." Also, Richard Neutra was working in Mendelsohn's office at the time. It was built to prove or disprove his theory of relativity, but if I remember right it was photographs taken elsewhere (Australia...?) that actually validated his theory. A series of plates (photos taken during a solar eclipse through a telescope in this case) that showed light bending around the Sun due to gravity. The full story of the repeated attempts to take such photographs and make the measurements is a great story in and of itself.