Time Out says
Flohmarkt Kanzlei is Switzerland's largest all year round flea market. You'll find everything here from cameras to clothing (excepting actual fleas, hopefully).
Switzerland's largest all year round flea market takes place every Saturday and boasts a variety of goods and vendors. From used mobiles, to collector's items like early 20th century cameras, from pensioners selling delicate china and parents offering the skis their children have grown out of, to local fashionistas cleaning out their wardrobes, there is something for everyone. Arrive early, roam through the stalls for an hour and then get a yummy breakfast at nearby café Dini Mueter.