Hin Nam No National Park

Hin Nam No is a block of tower karst pressed against the border, continuous with Phong Nha-Ke Bang on the Vietnamese side, and in 2025 it was added to that World Heritage property as a transboundary extension. The surface is a maze of blades and pinnacles with almost no soil, cut by dolines and drained entirely underground, so the rivers here run inside the rock rather than across it. Red-shanked douc and several cave-adapted species live in it, and much of the interior has never had a proper survey.

The landscape

• The karst towers - blades and pinnacles of grey limestone with sheer sides and forest on top.
• The dolines - collapse sinkholes hundreds of metres across, with their own forest inside.
• The cave systems - river passages including Xe Bang Fai, and many entrances not yet followed to their ends.
• The wildlife - red-shanked douc among the primates, and cave fauna found nowhere else.

When to go

November to April, when the trails are dry and the caves are enterable. From May the rain closes both, and the karst becomes dangerous rather than merely hard going. December to February is the coolest walking.

What to expect

There is no drive-in viewpoint: everything here is walked to, on rock that is sharp enough to tear boots. Treks are organised through the gateway villages with local guides, which is the arrangement the park is built around, and they need booking rather than arriving. Facilities are village-level and the interior is genuinely remote.

Nearby

The Xe Bang Fai river cave lies inside the massif, and Kong Lor cave is in the neighbouring karst to the north.

Key facts