The city as a living, breathing organism. I've seen a couple of these films now and I find them quite tough to judge, not in the least because they don't come with a dedicated score. There's no narrative here, so for a film that only relies on audiovisual elements the score is even more key than usual.
The version I watched didn't have any kind of score at all, which appeared to be a pretty good compromise at first, but didn't work out that well either. Films like this are quite poetic in nature (they call them city symphonies for a reason) and without a score the appeal diminishes quite a bit.
It's still rather nice to see a film that documents a bygone era, even when the technical qualities of the film heavily distort the reality it tries to capture. The editing is decent but not all that remarkable and 60 minutes may be a bit too long, but Ruttmann did a pretty solid job bringing Berlin to life. Without some proper music though, the second half got pretty boring.