There's an argument to be made that, with its lake, flower covered pedestrian bridge and medieval old city, Lucerne is the prettiest city in Switzerland and, considering that Switzerland is up there in terms of the beauty, possibly the world. Imminently walkable and full of cafes, shops and restaurants, Lucerne makes for a lovely day trip, usually offered as an optional or included excursion from Basel.
No matter what your interest, you'll find it in Lucerne. Love history? Stroll around the old city, take a walk on the city walls and visit the mournful Lion Monument. Art your thing? The Rosengart Collection has large collections of both Pablo Picasso and Paul Klee, buttressed by other pieces by Cezanne, Chagall, Kandinsky, Miro and Renoir. Train buffs will either want to visit the Swiss Museum of Transport or -- if you have enough time -- take the cogwheel train up Mount Pilatus; it's the world's steepest.
Much of Lucerne's appeal, however, is that you don't have to do anything to have an enjoyable day. Take a seat at a cafe, either on the lake or on Rathaus Quai along the Reuss River. Buy chocolate and gawk at the top-of-the-line (and oh so pricy) Swiss watches. Get a closer look at the nearby mountains by taking a sightseeing boat tour on Lake Lucerne. And make sure your phone is charged; Lucerne was made for Instagram.