This eye-catching lime-green neo-Gothic palace sitting in the Baía de Guanabara looks like something out of a child's fairy-tale book. It was designed by engineer Adolfo del Vecchio and completed in 1889. Originally used to supervise port operations, the palace is famous as the location of the last Imperial Ball on November 9, 1889. Today it's open for guided tours, which leave from the dock near Praça XV (Quinze) de Novembro. Purchase tickets from the Museu Naval.