Pier Luigi Nervi, 87, the international architect whose works ranged from cathedrals to sports palaces and was known for his use of reinforced concrete as a building material, died Tuesday at his home in Rome.

Among his works were the headquarters of UNESCO in Paris, the San Francisco Cathedral, three Olympic buildings in Rome, and the Cultural Center in Norfolk, Va.

Mr. Nervi's most recent project was the immense audience hall constructed in Vatican City under the direction of Pope Paul VI. The hall, which carried his name until Pope John Paul II renamed it the Pope Paul VI Hall, can accommodate 18,000 people under its soaring roof.

Mr. Nervi insisted that he was an engineer, not an architect. Commenting on his work, he once said, "Imagination is not involved. It is the natural laws of forces in equilibrium that determine the form and the structure. I do not invent anything."

His invention in the mid-1940s of ferro-cemento, a strong, light material composed of layers of steel mesh grouted together with concrete, made possible intricate building units for vast structures.

Mr. Nervi was born in Sondrio, Italy. He was a member of the architecture faculty of the University of Rome from 1946 to 1961.

His first large work, the Giovanni Berta Stadium in Florence, won international praise after its completion in 1932 for the elegance of its cantilevered stairs and roof.

His work attracted widespread attention during the Mussolini era for its sharp break with the heavy, boxlike neoclassicism favored by the fascists.

He was an admirer of the great builders of the Italian Renaissance and often spoke with particular praise of Brunelleschi, whose design for the dome of Florence Cathedral in the 15th century was a milestone in the spanning of space.

Mr. Nervi was quoted as saying that "their work, beyond being beautiful, was technically perfect. That does not mean that the great masters constructed by chance. Brunelleschi, before doing the dome for the Florence Cathedral, meditated for 10 years. That is also valid for modern architecture."

During the 1950s, Mr. Nervi's buildings included the Gatti wool factory and the railway station in Rome.

In 1961, he completed one of his most impressive projects, a labor palace for the exposition in Turin that encompassed an area greater than the Basilica of St. Peter, and had a volume of 2.3 million cubic feet.

Mr. Nervi also collaborated on the George Washington Bridge bus station in New York City from 1961 through 1962.