Taking into account the orthogonal division of architectural elements and the presence of the rectangular screen wall, for the decor of the walls and ceiling of this room Van Doesburg composed an oblique grid of squares, rectangles and triangles with the colours black, white, yellow, green, blue and red. Numerous sketches reveal the different stages of research for the decor of this 250 m room. Van Doesburg applied the aesthetic theories of Elementarism, the movement he founded in 1924, which affirm the use of the oblique in contrast to the Neoplasticism of Mondrian which was based on the use of verticals and horizontals only. The room benefits from unilateral natural lighting from the south thanks to five windows that overlook Place Kléber, reinforced by the lighting elements on the ceiling.
Salle des fêtes
For this decor Van Doesburg adopted an exclusively orthogonal composition animated by vertical and horizontal ligns that create squares and rectangles. The chromatic range consists of elementary colours (yellow, blue, red, black and white) dear to the Neoplasticist aesthetic. Two nuances of the same colour are juxtaposed to create a "discord". Certain modules hold enamel plates, each containing sixteen bulbs, thus creating artificial lighting. The original project included coloured linoleum flooring. The floor was finally done in parquet.
The trapezoid space of the foyer-bar was conceived by Van Doesburg as a hyphen linking the function room and the ciné-dancing. It was an open place in which the visitor could quench his thirst (a semi-circular bar was located against the north wall) while following the film projected in the ciné-dancing. The destination of this space corresponds to Van Doesburg's wish to encourage circulation between the different spaces so that the visitor might profit from the various leisure activities on offer. The decor of the foyer-bar was carried out by Sophie Taeuber-Arp. The composition is an arrangement of different rectangular flat tints with grey and red nuances. Van Doesburg drew a sketch for the floor which was certainly done in situ as it repeats the decor of the walls and ceiling.
Designed by Van Doesburg, the stairs provided access to the first floor from the mezzanine, and are situated in the position planned by Paul Horn in his blueprints.
In architectural terms, the stairs are situated in a rectangular cage and are composed of three flights and two landings. The painted decor is attributed to Sophie Taeuber-Arp and Arp. The long vertical stripes of grey and blue contrast with the broken ligns of the stairs and accentuate the upward movement. The stained glass window (the model for which is conserved in the Strasbourg Musée d'Art moderne et contemporain) was designed by Arp. It is composed of thirty tiles of rectangular cathedral glass with a range of tones in grey, blue and beige.