In January of 1978, I arrived in Frankfurt. For me, it was a New York City experience, without the massive scale of NY City. It didn't matter where you went....construction was underway....crowds of people were moving from through the town...and you stood in awe of the whole spectacle. HR built a timelapse piece of Frankfurt, and its worth a two-minute view.
The thing about Frankfurt as compared against NY City....is that the subway and trollycar line works like it should. The Airport has roughly 180,000 people that flow through each day. Roughly a hundred long-distance railway trains will come in or leave each day.
You have bankers and such who live more than an hour away from town, and make the trip in on a quiet railway car.....working off their laptop as they journey in. The Goethea-Frankfurt University has roughly 44,000 students.
I've been through Sydney, Vienna, Hong Kong, Melbourne, Amsterdam, Washington, New York, London, Paris, Rome, and twenty other major metropolitan cities. If I had to pick one single city with all the right features.....Frankfurt is it.