The Koło market takes place on Saturday morning in the neighborhood of Koło (hence its name), until 1pm. You have to take the tram to get to Koło - Ratusz Arsenal and the journey from the city center takes about 20 minutes. You can find everything there, from old junk to books and postcards! But there are plenty of nice things, such as antique furniture, paintings, musical instruments, military uniforms, medals and badges, coins and antique jewelry. But they are more expensive.