Most of the land area is situated on the valley between the Cordilleras and the Sierra Madre mountain ranges. The eponymous Cagayan River, the country's largest and second longest, runs through the region and flows from the Caraballo Mountains and ends at Aparri. Cagayan Valley is the second largest Philippine administrative region by land area. According to a literacy survey in 2013, 97.2% of Cagayan Valley's citizens (ages 10 to 64) are functionally literate, which is the highest out of all the regions in the Philippines, including the National Capital Region.