( CNN ) -- Brazil 's most influential modern architect Oscar Niemeyer , whose resume includes the United Nations building in New York , passed away on Wednesday . He was 104 . Niemeyer spent the last month in a hospital in Rio de Janeiro in frail health , according to his doctor Fernando Gjorup . Neimeyer died after suffering respiratory complications , Gjorup told reporters . Niemeyer was one of Brazil 's geniuses , said Brazilian President Dilma Rousseff . `` We have to dream , or else things wo n't happen , '' Rousseff said , using one of Niemeyer 's famous sayings . `` Few have dreamed so intensely and accomplished so many things like him . '' The president offered the presidential palace , one of Niemeyer 's well known designs , to his wife for his wake . Eduardo Paes , the mayor for Rio de Janeiro , has declared official mourning for three days . `` ( He was ) one of the greatest geniuses that Brazil gave the world , Oscar Niemeyer was more than a brilliant and innovative architect . He defied logic and twisted ways to create true works of art , '' Paes said . Born and raised in Rio , Niemeyer was an early master of modern architecture in Brazil , a fingerprint that became clear after he was commissioned alongside his mentor Lucio Costa to design Brazil 's new capital , Brasilia . Niemeyer `` incorporated curves and raw , unfinished materials '' with a `` balance between horizontal and vertical buildings , rectangular volumes , '' the United Nations Educational , Scientific and Cultural Organization said . Brasilia is a World Heritage Site . Among his other works are the presidential palace , the ministry of justice building and the presidential chapel . In Rio , his sinuous curves inspired the works of many poets , writers and songwriters . He designed the Sambadrome , where the samba schools hold their parades every year . In Sao Paulo , he worked with a landscape architect to build one of the largest city parks in Latin America , the Ibirapuera Park . Paes summed up what many felt when he said `` Brazil and the world lost today a man who dedicated his entire life to produce beauty . '' People we 've lost in 2012 : The lives they lived .
He was one of Brazil 's geniuses , the nation 's president says . Comment: The mayor of Rio de Janeiro called for three days of mourning .