The history of modern architecture owes a particular debt to the captains of industry (Pagano's first comment about this work, 1939) Industry is expressed by the building itself: unitary in its module, advanced in its building techniques, pioneering in its installations. The H-shaped plan, suggested by the difficult site, expresses the functioning of the building: the managers offices in the high central block are connected to the employees offices in the two side blocks, a representation of hierarchy which would not be found in the Pirelli building, and are served by the car-park in the open court at the front. The module on which the building is based (axes of 4,20 m) derives from the uniform size of the steel desks. This permits the use of movable partitions. The module is revealed to the observer by the pattern of windows on the facades. For the young Ponti the first Montecatini Building was a special opportunity, one that put his brain and his studio reinforced by two engineers to the test in a case of total design at a high technical level and on a large scale. The intense and stormy collaboration between the architect and the client (Guido Donegani, founder and president of the Montecatini company) raised the sights of both, and the building turned out not only to be efficient but also to have an image that achieved immediate popularity. The Montecatini image is not created by the solemn front set back, on a minor road but by the long sidewall on the main street. Perfectly level, with frames and windows set flush with the surface, this impenetrable wall appears without thickness (and already, in the Pontian manner, a sheet reflecting the sky), and the repetition in the openings seems, significantly, to be weightless.Aligned with the massive facade of the old Montecatini building, this airy wall (Malaparte and Savinio liked it) is an expression of the complete detachment of the two works of architecture. (It is a green and silver wall, made of marble and aluminium, Montecatini materials. About the marble Ponti said I have had the blocks crosscut, and I have invented a new kind of marble. He gave it the name Tempest.

The first Montecatini building was described in full by Casabella (130 pages were devoted to it, in 1939). Record-breaking speed of construction: twenty-three months, from November 1936 to September 1938. Exemplary installations, from the air-conditioning rare in Italy in those days to the advanced elevator and telephone systems — and Ponti did not want to conceal the beautiful plants, but to make them visible and visitable. Experimental use of aluminium alloys (in the window frames and roofing) and of mosaic gres facings (on the facades around the court). Appliances and fittings all revised, with enthusiasm by the designers, or designed by them for the purpose (and destined later for mass production, such as the SVAO sanitary appliances, designed by Ponti). For Ponti, the encounter with Montecatini also meant the beginning of a study of prefabrication: see the Montecatini ready-made staircases (designed by Libera, Ponti, Soncini, and Vaccaro).

As for the architecture of the building, Gio Ponti expressed doubts about it, years later: to what extent can this building, which relies for its image on a rhythmically end-less wall, and to which another story was easily added after the war, be called architecture, if architecture is as in the Pirelli building finite form. The building was subject to the dimensional constraints of the site and the building regulations we should look forward to a kind of city planning in which buildings, independent of frontal alignments, can be unitary, rational, correctly oriented, free from distortions.There were two images of this building that were particularly symbolic for Ponti: the foreshortened view of the airy sidewall and the interlacing of the colored tubes of the pneumatic dispatch system (my Leger»). The design of the building was the work of Ponti and the engineers Antonio Fornaroli and Eugenio Soncini Studio Ponti Fornaroli Soncini, with the collaboration of engineer Pier Giulio Bosisio.