Probably the first name that would spring into the minds of many of us, if asked for a great concrete architect, would be that of Pier Luigi Nervi. Here, in one man, is the genius of an architect, the efficiency of an engineer and the ingenuity of a contractor. Nervi's work has probably been subjected to more critical public appraisal than that of any other designer. One of Nervi's earliest jobs was the Florence Stadium opened in 1932. It is still noteworthy for its twisting staircase, then without precedent in concrete shapes. From this job, and the intricate curves of the staircase, Nervi concluded that there is a necessity to eliminate timber formwork. "Here , in effect," he says, "is a material which, by its monlithicity and its wonderful plastic adaptability, has widened beyond imagination the range of form in architecture." For his next major job, two Italian Air Force aircraft hangars built in 1935, he had not yet put his theories into practice. The reinforced concrete structure was designed by Nervi with economy in view, as a geodetic frame of intersecting curved ribs carried on a massive splayed support at each corner and acting together a as monolithic whole. As the calculations were so complicated, an approximate estimate was made and tested on a model. The years 1949 to 1952 were supremely active ones for Nervi. In general these years show a progressive trend towards his famed "light and airy" concept. The central circular roof for the rotunda at Ostia, for example, is carried like a lotus flower, petal between petal, on a single stem, and the independent peripheral roof is cantilevered from an exterior circle of columns. Of perhaps more current interest is Nervi's dramatic winged roof over the George Washington Bridge bus terminal in New York City. The scheme comprises two large reinforced concrete lattice beams along either edge of the building, and a longitudinal spine beams supported on a central row of columns. All the concrete was left as if came for the forms. Very great care was therefore taken in the choice of mix and the choice of formwork.