The most beautifull city in Switzerland is Luzern in english the call it Lucerne it is in the heart of Swiss on the very beautyfull Vierwaldstättersee.
This is not only my opinion it is the yearly statistic in which Lucerne get and got the most votes from the swiss people!
But I don't want to tell you that you should do like the Japanise people the make Switzerland in 3 days starting in Zürich at the Bahnhofstreet and then coming to Luzern and up to the Pilatus mountain of Luzern then go Berneroberland for Eiger, Mönch, Jungfrau the mountains of Berneroberland, then going to Zermatt and all this and sometimes even a bit more in 3 days! And I always like to see them flashing in the dark against Matterhorn with some little pixelhorses!
Have a nice trip!