One of my favorite activities when I am in Geneva during the weekend is to go to the flea market in Plainpalais. Since 1970, each Wednesday and Saturday, and also every first Sunday of the month, dozens of market stands showcase their precious objects to the public.
You will find crystal vases, old suitcases, beautiful paintings, furniture, old DVDs, vinyl and movies. Last time I went there I bought two beautiful lamps for CHF 10 each! Of course you have to look and search for the hidden treasures inside those cardboard boxes, but that is all part of the fun.
The flea market in Geneva is the perfect activity for a Saturday morning or Wednesday during your lunch break if you are working in Geneva; afterwards you can enjoy a great lunch in the area. Don’t forget to negotiate the prices; nothing is fixed ;).