The Río Quinto, also known as the Río Popopis, is a distinctive river system flowing through the heart of central Argentina, originating in the Sierra de San Luis near the Cerro Retama and Cerro Tomolasta mountains in San Luis Province. This endorheic river — meaning its waters do not ultimately reach the ocean — travels southeast across approximately 375 kilometers during dry periods and can extend to nearly 878 kilometers following heavy rainfall, a remarkable seasonal variability that defines much of the river's character. From its mountain headwaters, the Río Quinto descends through the sierras before transitioning into the Pampas, eventually dispersing into the Bañados de la Amarga wetlands in its lower course. Passing through the city of Villa Mercedes, where it reaches a width of roughly 45 meters, the river connects a diverse range of landscapes — from sierra terrain to open plains — and supports a rich network of wetlands and shallow lakes along its corridor through Córdoba Province.