The national park's botanical garden is a short drive from Phong Nha village and serves as the trailhead for several forest walks. The garden itself is modest — a collection of labelled native tree species and tropical plantings — but the surrounding primary forest is the real draw. Early morning here is good for primates: red-shanked douc langurs are occasionally seen in the canopy, and gibbons (rarely visible but sometimes audible) are present in the deeper forest.
A jungle trail from the garden leads towards the karst hillsides and a viewpoint with good sightlines over the park's western section. The botanic garden area is less crowded than the main cave circuit, and the forest quality is high. It's worth combining a visit here with the Nuoc Mooc Eco Trail for a full-day exploration of the western part of the park away from the main tourist flow.