Sơn Trà is a mountain of rainforest that rises straight out of Đà Nẵng, on the central coast of Vietnam, about 700 metres of it, ten minutes from the city's beach hotels. The forest is still there because the peninsula was a closed military zone through the Vietnam War, while the coast below it was built up. It is a nature reserve now, and it holds one of the largest populations anywhere of the red-shanked douc. The douc is a langur with crimson leg-stockings, a pale startled face and a grey coat, and primatologists call it the queen of primates. In the first hours after dawn the troops feed in the roadside canopy. You find one by riding the Hoàng Sa road slowly, engine off at the bends, watching the treetops for a flash of red legs with the sea behind.
That road switchbacks up from the shore into the forest, and every hairpin opens something else: a small cove below, the long curve of Đà Nẵng Bay, then forest again. Side tracks drop you to sand coves at the foot of the trees, Bãi Bắc and Bãi Rạng among them. The water runs clear there, and the city beach crowds are behind you. On the seaward cliffs a headland track ends at the old Tiên Sa lighthouse, where the forest gives way to bare rock and open water. It is the widest view you get on the peninsula. Near the southeastern tip stands a banyan reckoned to be about 800 years old, twenty metres high, holding its crown up on more than two dozen secondary trunks. At the southern foot the white Lady Buddha of Linh Ứng Pagoda looks out to sea, 67 metres tall, dwarfing the pilgrims in the courtyards below her. In 2016 a plan to build seaside resorts inside the reserve met fierce public opposition and was shelved, and the monkeys were a large part of why.