Cordillera Central (Luzon) Sierra Madre Mountains, the longest mountain range in the country, through the Caraballo Mountains in Nueva Vizcaya province. During Spanish colonial period, the whole range was called "Nueva Provincia", (New Province). The Cordillera Central is the highest mountain range in the Philippines. It comprises about 1/6 of the whole Luzon island with a total area of . The highest mountain in the range, Mount Pulag, is also the highest mountain on Luzon Island at . It is officially the third highest mountain in the country after Mount Dulang-dulang and Mount Apo on Mindanao Island, the second largest island of the
Apo Reef protection and conservation work at the park, stays in the protected area on weekly shifts. The largest is Apo Island at with mangroves and beach vegetation. The reef surrounding the island extends to in places. Outside the lagoonal mangroves in the eastern and southern sides of Apo Island, the soil is sandy-to-sandy loam that is less in silt and clay particles. On the other hand, the lagoonal mangroves have a sandy loam to clay loam soil, underlain by decomposed plant residues or coarse materials. Apo Island is separated from Apo Reef by a narrow, deep channel. The island is about