City Hall isn't a working station stop. It was boarded up in 1945, and, though there were plans to restore and reopen it as a transit museum, those plans were cancelled due to security concerns after 9/11. Though you can't stop there, if you take the 6 train to Brooklyn Bridge and don't get off, the train will then turn around in City Hall station.
Munich's U-Bahn system opened in 1971, just ahead of hosting the 1972 Olympics. Some of the station designs were very '70s-looking, favoring an orange and brown color palette. In the '80s and '90s, they began to update some of the stations, using bright colors to help distinguish them and make them look less similar to one another.
If you want to visit the Musée des Arts et Métiers, a museum of technological innovation, this is your stop. The museum, which exhibits over 2,400 inventions, is actually a part of the Conservatoire National des Arts et Métiers, a prestigious school in Paris dedicated to research in science and industry. When it was about to celebrate its 200th birthday, the station was redesigned to coincide with the celebrations. Belgian artist Francois Schuiten's steampunk design was meant to honor the work of Jules Verne.