Cat Tien National Park sprawls across 720 square kilometers in three provinces — Dong Nai, Lam Dong, and Binh Phuoc — about 150 kilometers northeast of Ho Chi Minh City. It is divided into two sections: Cat Loc to the north and Nam Cat Tien to the south and east, where the park headquarters and most visitor facilities are located. What makes Cat Tien exceptional is what it contains: rare lowland tropical forest, including areas of old-growth primary forest, of the kind that has been almost entirely cleared elsewhere in southern Vietnam. The forest type here — seasonal tropical, semi-deciduous, dense with climbing lianas and punctuated by stands of massive dipterocarps — was once common across the region. Now it survives in fragments, and Cat Tien is one of the largest. The park was first protected in 1978, giving it a head start on conservation that much of the surrounding landscape did not have.

In 1992, wildlife surveys in the Cat Loc sector of the park detected something unexpected: a small population of Javan rhinoceros, a critically endangered subspecies found nowhere else in mainland Southeast Asia. The discovery triggered the incorporation of Cat Loc into the park's protected area, creating a sanctuary around animals that numbered fewer than ten individuals. Conservation organizations worked with Vietnamese authorities for nearly two decades to protect them. It was not enough. Poaching continued, and the population — isolated, small, genetically stressed — dwindled. The last Vietnamese Javan rhinoceros was found dead in Cat Loc in 2010, its horn removed by a poacher's knife. Scientists confirmed the subspecies' extinction in 2011. The Cat Loc sector remains protected, its forests intact, home now to other species. The rhinoceros does not come back.

On the northern bank of the Dong Nai River, just outside the Nam Cat Tien sector, archaeologists working between 1994 and 2003 uncovered something that rewrote a corner of Southeast Asian history. A group of temples — belonging to a Hindu civilization previously unknown to scholarship — emerged from excavations that yielded gold, bronze, ceramic, colored stone, and glass artifacts spanning perhaps five centuries, from the 4th to the 9th century CE. Who built these temples, and what became of them, remains a matter of research and conjecture. The artifacts are now in the Da Lat museum. The site itself sits in the jungle at the park's edge, a reminder that the forest has been absorbing human history for a very long time, and that what it holds is not always visible from the trail.

Cat Tien's wildlife rewards patience and an appetite for the hours before and after daylight. The golden-cheeked gibbon, the park's signature species, sings at dawn. Siamese crocodiles — one of the rarest crocodilians in the world — can be seen at Crocodile Lake in the late afternoon and evening. Gaur, the massive wild cattle of Southeast Asia, move through the forest at night and are best spotted on night safaris. Deer and civet cats ghost through the undergrowth. The forest canopy holds a startling diversity of birds; the Hornbill bar at Forest Floor Lodge takes its name from the Oriental-pied and greater hornbills that cross the Ben Cu rapids at dusk. In the wet season, from mid-May onward, clouds of butterflies emerge as the forest greens up and the trees flower, and the air smells of rain and growth and something ancient.

Entry to Cat Tien requires a ferry crossing of the Dong Nai River — the park is on the far bank from Nam Cat Tien village, and the river is the boundary between the human world and what the forest protects. The first ferry runs at around 6:30 in the morning; the last return crossing leaves at 7 in the evening. Inside, trails branch through the forest to Crocodile Lake, to Ta Lai, to the elephant hills in the southwest. Bicycles can be rented for exploring the main roads. The Dao Tien Gibbon Sanctuary, run by a British conservation organization called Go East, rehabilitates gibbons, black-shanked doucs, silver langurs, and slow lorises on an island in the river. The work is serious and ongoing, conducted by people who spend their careers trying to give these animals a second chance at wild lives. The forest is still here. That is itself a kind of answer.