Never mentioned in his books, but always remembered as one of his most cherished works, the Augusteo cinema-theatre confirms Pier Luigi Nervi's ability to juggle daring hyperstatic structural solutions whose control is entrusted more to intuition and practical experience than to rigorous preventive calculation. In this work he further pushes forward research into three-dimensional reinforced concrete framework systems, conceived as resistant skeletons integrated with load-bearing masonry.

Located in the dense fabric of the historic centre of Naples, the building is the result of a modern real estate operation on the Vomero hill. The author of the project is the Roman architect Arnaldo Foschini, who turned to Nervi and Nebbiosi for the difficult execution of the roof. Nervi is thirty-five years old and is by now an established designer-entrepreneur who has already tried his hand several times with challenging roofs for large public spaces when he worked for Attilio Muggia's Sacc. Moreover, with Nervi and Nebbiosi, he has just completed the innovative 24-metre span reinforced concrete roofing of the Banchini Theatre in Prato.

The Naples project, however, is more complex. The most significant structure is the roof of the vast 30-metre diameter hall with an openable circular skylight in the centre, consisting of a radial system of 18 reticular beams from which tapering brackets cantilever, connected at the tip by a ring delimiting the central void. The height of the beams corresponds to the entire habitable top floor, and the diagonal struts are concealed in the partition walls of the office spaces. The horizontal connections between the pillars, along the inner perimeter of the hall, are joined at the corners to form a large annular Vierendeel beam that contributes to the torsional stability of the system. Finally, the two floor and roof slabs stiffen the structure in the horizontal plane.

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.

Between 1935 and the war years, Nervi and his company built several reinforced concrete airplane hangars for the Regia Aeronautica militare. Eight arose from the development of a single design for a ribbed pavilion vault with a geodesic structure, consisting of a set of 45° crossed arches with a maximum span of 50 m. Nervi arrived at this solution after a series of successive elaborations, initially studied for the Ciampino airport in 1935, starting from much more traditional schemes with portal and crossed reticular beams. For the first time, it made use of tests on scaled-down models carried out at the Milan Polytechnic by Guido Oberti to verify the suitability of the structural concept and refine the executive design. The first two airfields (1935-1938), entirely cast in situ, were built for the Orvieto military airport; the next six (1939-1942), distributed between Orvieto, Orbetello and Torre del Lago, follow the same geometric matrix as the first, but propose a drastic rethinking of construction processes: realised through the assembly of prefabricated lightened reticular structure elements, with only the integration of solid wall stiffening ribs in the most stressed areas, they anticipate the great use of structural prefabrication that Nervi would make in the post-war period.

Robust, built to last and resist wartime attacks, they were short-lived: all were demolished by German bombers in 1944. However, thanks to the spectacular images taken by the Vasari studio during and after the construction sites, they were not condemned to oblivion. After having edited their presentation in various architectural magazines between 1938 and 1941, Nervi always presented them as paradigmatic examples of an intuitive way of designing, capable of challenging conventions and as one of the first demonstrations of the potential of reinforced concrete in the field of large roofs. The exceptional nature of the aviorimessa should also be read in the light of the very special conditions of the Italian building industry in the pre-war autarchy years.

Designed and built immediately after the end of the war, Hall B of the Palazzo delle Esposizioni in Turin represents Nervi's first concrete opportunity to apply the principle of structural prefabrication, combining in a large-scale vaulted structure his highly personal use of ferrocement (wire mesh and small diameter steel rods embedded in a thin layer of cement) with the extensive use of prefabricated elements. It is also the first project that links Nervi to the great industrial clientele of Turin and Fiat. The Società del Palazzo delle Esposizioni, had commissioned the engineer Roberto Biscaretti di Ruffia to build on the remains of the Palazzo della Moda, designed in 1936 by Ettore Sottsass and then bombed, an exhibition hall to serve as a showcase for Turin's automobile industry. In 1947, Nervi e Bartoli won the competition by invitation and proposed two substantial variants to Biscaretti's design, which was based on a large apsidal hall: sloping side pillars, so as to widen the span of the vaulted ceiling, and, for the terminal apse, a thin lowered semi-dome as an alternative to a flat roof.

For the construction of the vault, Nervi designed prefabricated ferroconcrete wave elements, mounted on tubular reinforcement and made integral by reinforced concrete ribs cast along the ridges and recesses of the waves. Elegant fans each connect three arches of the wave roof to the inclined pillars. The apsidal semi-dome, on the other hand, is made of lozenge-shaped ferrocement tiles, which act as non-returnable formwork, like the ribbed pavilion roof over four inclined arches of the next and adjacent hall C (1949-50).

Inaugurated on 15 September 1948 and advertised as 'the most beautiful building Italy has ever built', Salon B attracted the attention of the international trade press as early as 1949, when it appeared on the cover of 'La technique des travaux'. Between 1953 and 1954, it was enlarged by five bays, which definitively obliterated the inner colonnaded garden. Between 1952 and 1953, Nervi worked out a project with architect Ettore Sottsass for a further extension with a 100 m span arch on the main front, but it was not followed up due to Sottsass' death in 1953. Resubmitted to the Società Torino Esposizioni in 1959 and approved by the building commission, it was shelved by the Company, which opted for a new underground hall designed by Riccardo Morandi.

In 1952, Marcel Breuer, Bernard Zehrfuss and Pier Luigi Nervi, under the supervision of an international team of five architects (Lucio Costa, Walter Gropius, Le Corbusier, Ernesto Rogers and Sven Markelius) were commissioned to build the Unesco headquarters in Paris on Place de Fontenoy, opposite the military school and the Eiffel Tower.
As representatives of the Ciam (International Congress of Modern Architecture), their intention from the outset was not to miss the opportunity to make it a manifesto of the main principles of modern architecture, as was the case with the UN's Glass Palace.

The complex consists of three buildings on a site of 7,722 square metres. The 7-storey Y-shaped Secretariat is elevated on 72 pilotis 5 metres high, skilfully sculpted by Nervi, which earned him the nickname 'Michelangelo of reinforced concrete' given to him by the newspaper France Soir. The facades, on the other hand, are treated differently according to their orientation.

But it is especially in the Hall of General Assemblies and Commissions that Nervi's contribution emerges. Characterised by a single concrete shell forming the walls and roof that is folded accordion-like and therefore resistant in shape, the roof rests on a transverse beam supported by six pillars and on the side walls. The shafts of the pillars, following a geometry dear to Nervi, have a ribbed surface with a double curvature obtained by the transition from a circular section at the base to a rectangular one at the top. The third building, a four-storey cubic volume, also on pilotis, and echoing the same façade composition as the Secretariat, was added at a later date. The fourth building was never constructed.

Many recognise Unesco's unprecedented plastic and technical strength in which Nervi's role stands out, proclaiming here in a palace of international representation that concrete majesty he had always sought.

Seen as a symbol of integration between structural and architectural invention and conveyed in leading national and international magazines, the Palazzo del Lavoro has fascinated entire generations. In emphasising, with a certain mannerism, the over-exhibited role of the structure, to the third phase of Nervi's design activity, that of the large international commissions in which the 'Nervi style' became a repertoire of solutions to be used worldwide.

The contract-competition for the construction of the 47,000 square metre pavilion that, for the Centenary of the Unification of Italy, was to host the great exhibition on labour presided over by Giovanni Agnelli and designed by Gio Ponti, was announced in July 1959. In October, the jury awarded the contract to the firm Nervi & Bartoli, with designers, in addition to Nervi, his son Antonio and Gino Covre, one of Italy's leading metal structure engineers. The project is centred on the subdivision of the square roof into sixteen independent umbrella-shaped elements of 40 metre sides separated by continuous strips of skylights and consisting of a radius of steel beams and a central pillar of variable geometry, a recurring feature in Nervi's works from the Corso Francia viaduct in Rome (1960), to the Savona railway station (1961) and the vault of San Francisco Cathedral (1970). The perimeter gallery, on the other hand, consists of isostatic ribbed floors typical of Nervi's work, made with mobile ferrocement formwork, according to a procedure already widely experimented by Nervi in various buildings including the Lanificio Gatti (1951-53). The proposal is convincing for its simplicity and structural legibility and, thanks to the modular solution and the differentiation of materials, is the only one capable of guaranteeing compliance with the very tight construction schedule. As had been the case for Torino Esposizioni, the construction management is ensured by FIAT's Construction and Plants Division, headed by Bonadè Bottino, with whom a relationship of mutual trust had been established. Apart from the technical data, which is nevertheless impressive - 158 metres wide by 26 metres high and 650,000 cubic metres in volume - the most innovative aspect is in fact the site organisation. Started in February 1960, by the end of December the building was already finished.

Made famous during the 1960 Rome Olympics, the Palazzetto is emblematic of Nervi's 'second life', that of the post-war period, centred on experimentation with ferrocement and structural prefabrication.

Conceived as a prototype of a medium-sized, inexpensive sports palace, to be offered identically in every city in Italy, it only later became part of the Olympic works, of which it soon became one of the best-known symbols.

In 1954, the Italian National Olympic Committee commissioned architect Annibale Vitellozzi with the project, who called Nervi for the roof structure. The concept is essential: a large circular dome 60 metres in diameter raised on inclined trestles set on an external circumference of 78 metres.

The minutely ribbed roof, which would have been too costly to construct on site using traditional techniques, will now use prefabricated ferroconcrete elements according to Nervi's patented system, for which the company Nervi e Bartoli is the exclusive concessionaire, and will therefore be entrusted with the construction.

Having abolished the wooden ribs, Nervi, as he had already done with the second series of aviorimittas, broke the canopy down into pieces to be fabricated on site, which were then assembled on a light, discontinuous scaffold; in the channels between the planks, the reinforcement was then placed and the completion cast. Costing a mere 200 million lire, it was built in just over a year.

Critical acclaim is controversial. The Italian architectural culture reacts without enthusiasm: only the critic Bruno Zevi publishes it immediately, but on the whole criticism prevails, questioning all public works hastily constructed for the Olympics. Instead, the world's specialist press, far from political polemics, competed for photos of the small masterpiece, decreeing Nervi's definitive recognition at the top of the international engineering scene.

The Montréal Stock Exchange Tower is one of four skyscrapers constructed by Nervi: the Pirelli (1955-1958) in Milan with Gio Ponti, and, in Sydney with Harry Seidler, the MLC Centre (1971-1977) and Australia Square (1963-1965).

In the late 1950s, Montréal attracted many Canadian and foreign investors. Webb & Knapp was building the Place Ville-Marie (1957-1966) to a design by Ieoh Ming Pei, while the most important Italian construction company, the Società Generale Immobiliare, associated with the Banque Mercantile du Canada had commissioned Luigi Moretti and Nervi for the new Stock Exchange headquarters in Place Victoria.

The first project, released in August 1961, was one of the most ambitious: three 51-storey square towers set diagonally on top of a four-storey base above ground. The final project, revised for geological, regulatory and commercial reasons, and dated November 1962, ended up comprising only two twin towers of 48 storeys and 190 metres in height located on the initial part of the block and separated by a low building. Only one of the two towers will be built, but the construction will be very fast, just 351 days!

Nervi and Moretti, in very different ways, share the conviction that structure must be the basis of architecture. By exposing the framework in the façade, Nervi diversifies and hierarchizes the elements. The tower, enveloped in a light curtain wall of glass and aluminium, is dominated in expressive terms by the incisive presence of the pillars rising from the ground at each corner and by the complex geometry of its volume, at once pot-bellied and tapered. The load-bearing structure, consisting of a central core connected to the four corner pillars by three gigantic lattice girders on the fifth, nineteenth and thirty-second floors, is designed to make the framework less cumbersome and more resistant to the stresses caused by lateral wind pressure and earthquake tremors. This scheme was masterfully employed by Moretti, who exploited it to emphasise the tower's verticality, and to give the shaft an entirely classical rhythm, thus moving away from the prismatic skyscraper model.

From the first months of his pontificate, which began on 30 June 1963, Paul VI had great confidence in the design of the new hall for the general audiences in the Vatican. It was he who directly called Nervi, who responded by drawing up an initial project as early as September 1963. The layout was defined at the beginning of 1964: a large volume with a trapezoidal plan covered by an undulating vault with a parabolic profile supported, on the entrance side, by ten white concrete pillars and, on the other side, by a hollow beam resting on two inclined pillars framing the papal throne. The hall, approximately 80 m wide and 100 m deep, with a maximum height of 18 m, is designed for a maximum capacity of ten thousand seats. The vault is realised with the system already adopted several times with prefabricated corrugated elements that serve as formwork for the casting of the ribs. Characteristic of the building is the white concrete with white marble grit.

Due to construction difficulties in the cramped spaces of the Vatican, the building site only started at the end of 1966 and was completed in 1971. In the years that saw the slow completion of the work, Nervi devoted himself to defining the ceilings and the glass eye, which only after a few variations reached its final oval shape, ribbed on the inside.

In keeping with Paul VI's intentions, the Vatican hall is not a church, but retains some of its fundamental requirements: the excellent visual and aural functionality, but also the 'severe, structurally comprehensible and distraction-free environment', the moderate lighting and the few easily intuitable images. Thanks to the planimetric configuration, the thickening and rising of the covering waves and the intensification of the lighting, the papal throne is the only visual and symbolic focus of an almost immeasurable space, which was only completed in 1977 by Pericle Fazzini's La resurrezione di Cristo group.

With the design of St. Mary's Cathedral, Nervi, commissioned as structural design consultant by his friend architect Pietro Belluschi, dean of architecture at the Massachusetts Institute of Technology and consulting architect for the local firm McSweeney, Ryan & Lee, did not hesitate to take up the challenge of testing his own experiments on structures for a very innovative work in a highly seismic area.

The project is characterised by its hyperbolic paraboloid dome, reminiscent of those in Kenzo Tange's cathedral in Tokyo but also those studied by Eduardo Catalano, Belluschi's friend and colleague at MIT. Arranged in the shape of a Greek cross, the 42 metre high paraboloids rest on profile arches and triangular sections that bear the load on four sculptural sloping pillars. Reinforced by exposed ribs on the inner face, the paraboloids are built using the usual system adopted by Nervi of prefabricated ferroconcrete tiles, here shaped into triangles, and cast in-situ completion. The result, on the inside, is an elegant triangular weave warped according to the crooked horizontal straight lines of one of the two families of generators of the paraboloids, and spatial curved lines for the ribs that espouse the double-curvature configuration.

Almost as if to emphasise the geometric foundations of the spatial concept, the covering of the dome in travertine slabs is instead marked by the double mesh of crooked straight lines that generates the double-curved surface of the parabolids.

The model experiments conducted at Ismes between 1964 and 1965 are for Nervi the test-bed for his structural intuition. The results, attesting to its validity, would be confirmed by computer verifications on the basis of advanced numerical modelling by Robinson & Associates, who were locally responsible for the executive project, and the Californian auditors.

In the execution phase, however, Nervi's role ends up fading, although he even plans to ship the prefabricated pieces of the dome from Rome to San Francisco.

Between this last attempt to control the construction site and the surprise of seeing the intuitions tested on experimental models verified on the computer, the end of a world almost came. Engineering has become engineering and a family-run firm like Nervi's has little hope of survival, despite its irrepressible international fame. St. Mary's is the swan song not only of the Nervi studio but of an entire season of civil engineering.