Rietveld worked on several well-known Gispen furniture pieces, including the President office chair, and several light fixtures. He enjoyed a lot of artistic freedom at Gispen. His most well-known design is probably the Mondial chair, which he devised together with his father, Gerrit Rietveld. The stackable and linkable, delicate K-shaped chair was specifically created for Expo 58 in Brussels. It was intended to be fully executed in aluminum, but apart from a few prototypes this was not followed through at that time, as that was not yet technically possible. Gispen produced the chair's seat in polyester, against Rietveld's wishes. Shortly afterwards, Rietveld quit his position at Gispen.