The article tells the history of the design of the Moorish Pavilion, headquarters of Fundação Oswaldo Cruz (Fiocruz), completed in 1918. The year 2021 marks the fortieth anniversary since its listing by the Brazilian heritage protection agency, Instituto do Patrimônio Histórico Nacional, as one of the most representative examples of eclectic architecture in Brazil. Designed by the Portuguese architect Luiz Moraes Jr., its aesthetic, formal, spatial, and functional features derive from multiple influences, which consolidated its recognition as Brazilian cultural heritage. The urban setting in which it was built, in Rio de Janeiro, is also analyzed, and the revision of the historiography of Brazilian architecture, instrumental in the recognition of its cultural and scientific value, is appraised.