Flowing through the heart of the Biobío Region, the Río Andalién is an urban and peri-urban river that winds its way through the city of Concepción and the surrounding comunas of Florida, Penco, Talcahuano, and Chiguayante before emptying into the Bahía de Concepción at Playa Negra near Penco. The river originates from the confluence of two smaller waterways — the Estero Poñén, which drains from the northern divide of the Cordillera de la Costa, and the Estero Curapalihue, which flows in from the south. Spanning approximately 36 kilometers in length and draining a watershed of roughly 780 km², the Andalién is a coastal range river, meaning it is fed by rainfall and runoff from the Chilean Coastal Mountains rather than Andean snowmelt. The river meanders through numerous bends and low hills of the coastal range before flattening into an alluvial plain near Concepción, where it frequently divides into multiple braided channels before reaching the bay. Despite its urban setting, the Andalién supports a surprising variety of fish life, including both native Chilean species and introduced sportfish, making it an accessible option for anglers based in or near Concepción.