The headliner is Catch That Zeppelin, an alternate history-esque vignette of 1930's New York City, as seen through the eyes of zeppelin engineer Adolf Hitler. Not really that good a story - Fritz himself allows that it was awarded the Nebula and Hugo "to comfort my old age -- old people do have an advantage in such competitions, if they can manage to function at all." But there's a detail that provides some extra weirdness to the story. The bullk of the story relates the details experienced by the narrator after being thrown back into a 1930s NYC with a zeppelin moored at the Empire State Building, the tallest building in the city. At the end of the story, the narrator is thrown back into the present:
When I at last fully came to myself, I was walking down a twilit Hudson Street at the north end of Greenwich Village. My gaze was fixed on a distant and unremarkable pale-gray square of building top. I guessed it must be that of the World Trade Center, 1,350 feet tall.
It seems his 'present' is yet another, possibly happier, alternate history.