Jules Dassin's The Naked City (1948) was cutting edge when it was made, all on location, almost a documentary crime story. There are eight million stories in the naked city, this movie looks at a lot of them.
The main story is about a murdered model. The police, Barry Fitzgerald and Don Taylor, investigate and find plenty of shady characters, including Howard Duff. By the end, they have found the culprit and justice has been served.
But while all of this is going on, we are treated to a tour of the city - the streets, the tenements, the docks, newsstands and subways. Dassin "stole" a lot of this footage - the technical term for filming covertly on location, using the passersby as extras. I don't know how this went down in 1948 - my guess is that people felt a shock of recognition, immediacy, like they could see themselves. Now, it's more like a museum of New York, a sort-of-ordinary police procedural wrapped in a lovely documentary.
Sort of off-topic, but there was a thread on Movie Morlocks about how creepy Barry Fitzgerald is, with his professional Irishman mannerisms. I had that in mind while watching this, and I could really see it.