The Cuc Phuong NP lies in northern Vietnam. It is a scenic forested limestone upland around 120km SW of Hanoi. There is a national park HQ that organises guides and excursions to the main sites. One can stay right in the park as there is a simple but more than adequate guesthouse and a restaurant. The staff are very helpful. Special wildlife includes the rare primate Delacour's Langur and Red-collared Woodpecker. It is a place to take one's time, walking and trekking in search of wildlife, with mornings and evenings definitely best.
Before joining any wildlife watching or birding tour, wherever in the world, try to establish if the travel company you are considering booking with operates in an environmentally friendly, responsible manner.