Each mountain is named for the natural element it’s said to represent: Thuy Son (Water), Moc Son (Wood), Hoa Son (Fire), Kim Son (Metal or Gold) and Tho Son (Earth). The villages that have sprung up at the base of the mountains specialize in marble sculpture, though they now astutely use marble from China rather than hacking away at the mountains that bring the visitors (and buyers) in.
Thuy Son (admission 15,000d; 7am-5pm) is the largest and most famous of the five mountains, with a number of natural caves in which first Hindu and later Buddhist sanctuaries have been built over the centuries. Of the two paths heading up the mountain, the one closer to the beach (at the end of the village) makes for a better circuit.
At the top of the staircase is a gate, Ong Chon, which is pockmarked with bullet holes. This leads to Linh Ong Pagoda. Behind it, a path heads left through two short tunnels to several caverns known as Tang Chon Dong, containing several Buddhas and blocks of carved stone of Cham origin. Near one of the altars is a flight of steps leading up to another cave, partially open to the sky, with two seated Buddhas in it.
Immediately to the left as you enter Ong Chon Gate is the main path to the rest of Thuy Son, beginning with Xa Loi Pagoda, a beautiful stone tower that overlooks the coast. Stairs off the main pathway lead to Vong Hai Da, a viewing point that would yield a brilliant panorama of China Beach if it weren’t so untended. The stone-paved path continues to the right and into a canyon. On the left is Van Thong Cave, opposite which is a cement Buddha and a narrow passage that leads up to a natural chimney open to the sky.
Exit the canyon through a battle-scarred masonry gate. There’s a rocky path to the right leading to Linh Nham, a tall chimney-shaped cave with a small altar inside. Nearby, another path leads to Hoa Nghiem, a shallow cave with a Buddha. If you go down the passageway to the left of the Buddha, you come to cathedral-like Huyen Khong Cave, lit by an opening to the sky. The entrance to this spectacular chamber is guarded by two administrative mandarins (to the left of the doorway) and two military mandarins (to the right).
Scattered about the cave are Buddhist and Confucian shrines; note the inscriptions carved into the stone walls. On the right a door leads to two stalactites, dripping water that comes from heaven, according to local legend. Actually, only one stalactite drips; the other one supposedly ran dry when Emperor Tu Duc touched it. During the American War this chamber was used as a VC field hospital. Inside is a plaque dedicated to the Women’s Artillery Group, which destroyed 19 US aircraft from a base below the mountains in 1972.
Back on the main path, just to the left of the masonry gate is Tam Thai Tu Pagoda, restored by Emperor Minh Mang in 1826. A path heading obliquely to the right goes to the monks’ residence, but before you reach it, take the stairs to the left of the path to Vong Giang Dai, which offers a fantastic 180-degree landward view of the other Marble Mountains and their surroundings.
A torch (flashlight) is handy but not essential for exploring the caves. The gradient of the walk is quite comfortable, but whichever end you start at, the ascent up the mountain begins with a fairly strenuous climb. Local buses between Da Nang and Hoi An (tickets 10,000d) can drop you at Marble Mountains, 19km north of Hoi An.