The mountain massif that Virachey protects is the lower extremity of a geological structure that runs down from Tibet through the length of mainland Southeast Asia. Until 1903, this entire range belonged to Laos. The French, reorganizing colonial administration, decided to transfer Stung Treng Province to Cambodia and draw the border between Laos and Cambodia along the high ridgeline, extending east to Vietnam. The result was a political boundary that cut across an ecosystem — and the park that Cambodia eventually created here in 1993 preserves one of the largest continuous blocks of lowland and montane forest remaining in the region. The park spans both Ratanakiri and Stung Treng Provinces, anchoring the northeastern corner of the country against the mountain frontier.

Virachey's terrain shifts as you move through it: river valleys dense with evergreen forest give way to bamboo groves and then, at elevation, open high grasslands where the views stretch for enormous distances. The Sesan River runs along the park's southern edge, with Brao and Kreung minority villages dotting the banks — communities whose people have lived alongside this forest for generations. Within the forest itself, the animal life is remarkable: gibbons call across river valleys, pig-tailed macaques and douc langurs move through the canopy, sun bears forage at low elevation. Great hornbills — large, slow-flying birds with enormous curved bills — are present. Clouded leopards and Asian elephants roam the deeper reaches. Whether tigers and leopards still survive in meaningful numbers is genuinely unknown.

From 2004 to 2008, the World Bank funded a conservation program in Virachey. When the program ended, so did the patrols. According to park rangers, not a single patrol went out in all of 2009 — and the same was likely true in 2010. Illegal logging and poaching are chronic threats. The more acute threat, as of the time of writing, is the prospect of a Chinese-funded road being bulldozed through the southwestern corner of the park. No formal road plans have been publicly announced, but the pressure to open these forests to development is real and ongoing. A park that exists on paper but cannot be patrolled is vulnerable in ways that border maps cannot express.

Access to Virachey begins in Ban Lung, the capital of Ratanakiri Province, where trekkers register at the national park office and arrange guides. The route to Veal Thom Grasslands — the park's signature destination — is described as a kind of mini-Annapurna: a week-long journey into a landscape that few people reach and fewer still photograph. The grasslands themselves are described as jaw-dropping, the views opening onto wild mountainous borderland with Laos and Vietnam in every direction. Nights are spent in hammocks; meals are cooked over fires in the jungle. The indigenous guide, a member of one of the local minority communities, carries knowledge of the forest that no map contains. Trekkers carry their own hammock — light, spacious, provided with park entry — and extra food.

Along the Sesan River's edge, Brao and Kreung villages have existed in a relationship with this forest that predates the park, predates Cambodia as a nation, and reaches back into a past that archaeology has only begun to document. These communities are not background scenery. They are the people who know the forest most intimately — the indigenous guides who lead treks carry knowledge accumulated across generations of living alongside clouded leopards and sun bears and gibbons. The park's ecotourism program, imperfect and underfunded as it has been, represents an attempt to align conservation with local livelihoods. When travelers purchase handwoven scarves from a minority village at the start of a trek, the transaction is small; the signal it sends — that this forest and its people have value — is not.