Just south of Da Nang on Vietnam’s central coast, the Marble Mountains (Ngu Hành Sơn) rise like ancient sentinels above the surrounding flatlands. These five striking limestone and marble hills are each named after one of the five elements of Eastern philosophy: metal (Kim), wood (Mộc), water (Thủy), fire (Hỏa) and earth (Thổ). Steeped in legend and spirituality, the mountains have long served as places of worship and retreat.