More Photos Mar del Plata is a city on the coast of the Atlantic Ocean, in Buenos Aires Province, Argentina. It is the seat of General Pueyrredón district. Mar del Plata is the second largest city in Buenos Aires Province. The name "Mar del Plata" is a shortening of "Mar del Rio de la Plata," and has the meaning of "sea of the Rio de la Plata basin" or "adjoining sea to the (River) Plate region". Mar del Plata is one of the major fishing ports and the biggest seaside beach resort in Argentina. With a population of 682.605 as per the 2022 census [INDEC], it is the 5th largest city in Argentina. Wikipedia