Río Aller is a river located in the province of Asturias, northern Spain. It flows through the Aller Valley and is a tributary of the larger Río Nalón. The river is approximately 30 kilometers long and is known for its scenic beauty, surrounded by lush forests and mountains. The river is popular for various outdoor activities, including fishing and hiking along its banks. Its waters support a diverse ecosystem, making it an important habitat for local wildlife. The surrounding area is also rich in cultural heritage, with several small towns and villages nearby that reflect the region's history.