"Portuguese explorers arriving at the mouth of Guanabara Bay on January 1, 1502 thought they had discovered the mouth of an enormous river which they named January River or Rio de Janeiro. By the time the first settlement was established and the error was realised, the name had already stuck."
The Corcodova Mountains hosts the statue of Christ the Redeemer, so huge that it became well- known throughout the world!
Source: Azzopardi, T., et al. Rough Guide to South America.