By Jeb Blount

RIO DE JANEIRO (Reuters) - Oscar Niemeyer, a towering patriarch of modern architecture who shaped the look of modern Brazil and whose inventive, curved designs left their mark on cities worldwide, died late on Wednesday. He was 104.

Niemeyer had been battling kidney ailments and pneumonia for nearly a month in a Rio de Janeiro hospital. His death was confirmed by a hospital spokesperson.

Starting in the 1930s, Niemeyer's career spanned nine decades. His distinctive glass and white-concrete buildings include such landmarks as the United Nations Secretariat in New York, the Communist Party headquarters in Paris and the Roman Catholic Cathedral in Brasilia.

He won the 1988 Pritzker Architecture Prize, considered the "Nobel Prize of Architecture" for the Brasilia cathedral. Its "Crown of Thorns" cupola fills the church with light and a sense of soaring grandeur despite the fact that most of the building is underground.

It was one of dozens of public structures he designed for Brazil's made-to-order capital, a city that helped define "space-age" style.

After flying over Niemeyer's pod-like Congress, futuristic presidential palace and modular ministries in 1961, Yuri Gagarin, the Russian cosmonaut and first man in space, said "the impression was like arriving on another planet."

In his home city of Rio de Janeiro, Niemeyer's many projects include the "Sambadrome" stadium for Carnival parades. Perched across the bay from Rio is the "flying saucer" he designed for the Niteroi Museum of Contemporary Art.

The collection of government buildings in Brasilia, though, remain his most monumental and enduring achievement. Built from scratch in a wild and nearly uninhabited part of Brazil's remote central plateau in just four years, it opened in 1960.

(Additional reporting by Brian Ellsworth; Editing by Todd Benson, Kieran Murray and Philip Barbara)