Rather than put this in the YouTube thread, I think it deserves one of its own. This is a 6-minute German newsreel feature, showing the build-up to the 1938 Tripoli GP. Although the commentary is in German, the amount of detail you can pick up from the pictures alone is astonishing. Close-up shots of Conti tyres' tread patterns, anybody? W154s being towed through the streets?
King Rose Archives have also uploaded some other German newsreels from the same era. The 1938 and 1939 German GP ones are particularly good - the former for what it doesn't show (Seaman on the podium) and the latter for some spectacular aerial shots, which emphasise just how big the Karussel actually is.