The Ho Chi Minh Trail — the supply network that kept the North Vietnamese forces fighting through the American War — ran through the valleys of what is now the national park. The mountains here were strategic: hard to bomb effectively, close enough to the Laotian border to receive supplies, and providing natural cover. Sections of the trail are still visible, and some supply depots, vehicle shelters, and bomb craters remain in the forest.
Local tour operators run motorbike trips along surviving sections of the trail. The combination of the landscape, the history, and the quiet of the forest — broken only by the occasional click of a jungle creature — gives these trips a different quality from the cave tours. The trail passes through villages of the Bru-Van Kieu ethnic minority, and some tours include a stop to meet local families. Ask your guesthouse in Phong Nha village about operators — most can arrange a half-day or full-day trip.