The Tinguely Fountain is right at the theatre in Basel. It is my favorite. With its many moving and spewing and splashing pieces, it is a view!
If you are coming in winter, you may be lucky and see it fully covered in ice, which gives it a fairy-tale feeling. (See picture.)
And if you really liked Tinguely's style, don't forget that there's a Tinguley museum in Basel, too!