The Berta stadium, thanks to the extraordinary critical acclaim and the presentation made by Pietro Maria Bardi in "Quadrante" and Giovanni Michelucci in "Architettura", is the work that allowed Nervi's entrance into the world of architecture, sealed by his participation in the exhibition of Rational Architecture in Florence curated by Michelucci himself with Adalberto Libera in 1932. In fact, Nervi showed a careful knowledge of the theoretical and design reflections of the Italian Rationalism movements (Miar and Gruppo 7), which would identify in him and in his undertaking, the possibility of managing new building techniques and the very terms of an architectural language, in the delicate passage from programmatic declarations to concrete experimentation.
Promoted by the Gruppo Rionale Fascista, the project, initially drawn up by the municipal technical office, was entrusted at the end of 1930 to Nervi & Nebbiosi, who a few months earlier had presented a daring proposal for the construction of the grandstand of honour: a reinforced concrete canopy with a 22.5-metre cantilever, resting on 15 load-bearing brackets with a curved section and stiffened by two transverse beams; a sort of static paradox in which equilibrium is achieved by virtue of the action of the beam and the counterweight of the steps.
An alternative project to the one known up to this point, to be dated 1930-31 and recently rediscovered, on behalf of an engineer in search of an appropriate architectural language that resorted to representational techniques typical of the figurative avant-gardes and with formal solutions comparable to certain contemporary elaborations by Adalberto Libera and Mario Ridolfi. The final project was in fact drawn up by Nervi in parts, between 1931 and 1932, the year in which he dissolved the partnership with Nebbiosi to found Nervi & Bartoli, and the covered grandstand, the tiers of seats, the helicoidal stairs and the Maratona tower were fine-tuned by Nervi as the building site progressed. In the new grandstands and the Marathon Tower he once again resorted to static paradoxes: in the staircase, a tapered slab, on which the steps rest, cantilevers from a helical beam, while balancing the stresses is another twisted beam, symmetrical and inverted, forming a spatial framed structure; while the tower, the 55 metre high glass spindle incorporating an exposed lift, rests on a cantilevered slab. In 1950-1951 Nervi was entrusted with the extension project: two 114 metre long elevated grandstands with four new spiral staircases.
