The Castagnino is the finest art museum in Argentina outside Buenos Aires, housed in a handsome French neoclassical building at the edge of Parque de la Independencia. The permanent collection spans European masters — including works by Goya, Rubens, and El Greco — alongside an extensive Argentine collection covering the 19th and 20th centuries.
The Argentine section is particularly interesting: Rosario produced a remarkable generation of avant-garde artists in the 1960s and the museum documents that experimental period well. Temporary exhibitions rotate throughout the year. The building itself, designed in the French academic style, is worth a look even from the outside. Open Tuesday to Sunday; admission is modest.