The Castagnino Municipal Museum of Art is the best art museum in Mar del Plata, housed in a handsome 1940 villa in the Playa Grande area. The collection focuses on Argentine art from the 19th century to the present, with a strong representation of the Mar del Plata school of painting and works by national figures including Benito Quinquela Martín, Antonio Berni, and the museum's namesake Juan Carlos Castagnino, a local painter celebrated for his social realist work.
The building itself, with its gardens and veranda rooms, is worth seeing in its own right. The museum is open Tuesday to Sunday; admission is modest, with free entry on Wednesdays. A small bookshop sells good reproductions.