Caso is a municipality in the Spanish Principality of Asturias. It shares a boundary to the North with Piloña; to the East with Ponga; to the Sou…Caso is a municipality in the Spanish Principality of Asturias. It shares a boundary to the North with Piloña; to the East with Ponga; to the South with León and to the West with Sobrescobio and Laviana.