Lucio Costa, 96, a noted architect and city planner who planned the Brazilian capital Brasilia, died June 13 at his home in Rio de Janeiro. His family reported that he "died in his sleep."

Brazilian President Fernando Henrique Cardoso declared three days of mourning for Mr. Costa.

Mr. Costa was born to Brazilian parents living in Toulon, France. He studied at the National School of Fine Arts in Rio de Janeiro.

A pioneer of Latin American modernist design, Mr. Costa was little-known outside architectural circles until 1957, when he won an international competition to design a new Brazilian capital to be built on the country's barren central plateau.

Under his novel design, Brasilia, which took over from Rio as the country's capital in 1960, was laid out in the shape of an airplane or cross.

Government agencies and ministerial buildings are built on either side of the main east-west axis, with the Presidential Palace, Congress and Supreme Court buildings at one end. The north-south axis houses residential districts.

The city was hailed as a monument to modern architecture. One of the world's newest cities, Brasilia is on UNESCO's World Heritage List, which includes the Great Wall of China and Venice.

Despite his role in designing Brasilia, Mr. Costa was always overshadowed by Oscar Niemeyer, the controversial architect who designed most of the important buildings in the new capital.

Mr. Costa's only standing construction in Brasilia is a television tower, a huge concrete and steel antenna of no remarkable architectural value.

Former President Juscelino Kubitschek, who governed Brazil from 1956 to 1960, hoped that moving the capital from Rio would encourage development in the country's interior. Mr. Costa seriously miscalculated how fast the new city would grow. Originally designed for no more than 500,000 people, Brasilia is now home to more than 2 million, mostly bureaucrats, lobbyists and politicians.

While admiring Mr. Costa's wide open spaces, many Brasilienses, as the locals are known, complain that the design is unfriendly to pedestrians, saying that the city is impossible to move around except by car.

A quiet, retiring man, Mr. Costa never again designed anything to compare with Brasilia and always seemed a little in awe of his greatest work.

Shortly after returning from one of his last visits to the city, he remarked to a friend: "The truth is, the dream was smaller than reality. And the reality was bigger and more beautiful than the dream."