The protected area, best known as the location of Callao Cave, covers the largest block of forest under conservation in the province.

It covers 118,781.582 hectares (293,515.68 acres) of the northern Sierra Madre mountain range and its adjacent Pacific coast.

The protected area is home to the Callao Cave Eco-Tourism Zone being promoted by the locals as the 'Caving Adventure Capital of the Philippines'.

[6] Callao Cave was visited by American Governor-General Theodore Roosevelt Jr. in 1932 who under his term created the National Park system of the country with the passing of Act No.

[1] With the passing of the NIPAS Act of 1992 that revamped the protected areas of the country, the Callao National Park was reclassified but enlarged by Proclamation no.

In 2003 upon the recommendation of the Department of Environment and Natural Resources (DENR), the protected area was further enlarged to include certain parcels of land in the public domain.

It extends along the northern Sierra Madre range from the Twin Peaks south to Mount Cetaceo towards the border with Isabela.

It covers 18 of the 24 barangays of Peñablanca, namely, Callao, San Roque, Cabbo, Nannarian, Malibagbag, Quibal, Agugaddan, Lapi, Nanguilattan, Nabbabalayan, Buyon, Mangga, Minanga, Sisim, Bugatay, Bical, Baliuag and Cabasan.

It is traversed by the Pinacanauan River, a major tributary of the Rio Grande de Cagayan, which supplies clean water and irrigation to surrounding communities as well as the nearby city of Tuguegarao.

To accelerate the development of the Callao Cave ETZ, the Provincial Tourism Office of Cagayan has tied up with several Non-Government Organizations (NGOs) such the Sierra Madre Outdoor Club (SMOC), Cagayan visitors bureau, souvenir makers, and other interested investors to help make Callao Caves tourist zone more develop and beautiful.

The SMOC also assists tourists in recreational activities like caving, spelunking, mountain climbing, trekking, kayaking, rappelling, swimming, circadian flight viewing, and picnicking.

The tourism office staff were also arranging some partnerships with other organizations and agencies to rebuild the deteriorating facilities of the Callao Caves cottages for trainings, seminars, conventions, and other uses.

[14] It has a walking passage, winding streams and various-sized pools, multi-depth shafts, and drops for many rope works.

San Carlos requires a lot of swimming because more than half the cave is covered by a cold running subterranean river.

[11] As a key biodiversity area, the park is home to several other threatened and restricted-range birds such as the flame-breasted fruit dove, spotted imperial pigeon, Isabela oriole, green racquet-tail, Philippine eagle-owl, whiskered pitta, Philippine duck, celestial monarch, Luzon water-redstart, ashy-breasted flycatcher, and green-faced parrotfinch.

[11] The park's forest cover is composed of Dipterocarp trees such as narra, molave, agosip, ipil-ipil, balete, tindalo and anabiong.

The DPWH and DOT are mandated to develop and enhance road networks leading to tourism sites by virtue of Republic Act No.