The Perfume River (Sông Hương or Hương Giang; 香江) is a river that crosses the city of Huế, in the central Vietnamese province of Thừa Thiên–Huế Province. In the autumn, flowers from orchards upriver from Huế fall into the water, giving the river a perfume-like aroma, hence the soubriquet.
The Perfume River has two sources, both of which begin in the Dãy Trường Sơn mountain range and meet at Bằng Lãng Fork. The Tả Trạch (left tributary) originates in the Trường Đồng mountains and flows northwest towards the fork.
The river then flows in south-north direction past the temples of Hòn Chén and Ngọc Trản, then flowing north-west, meandering through the Nguyệt Biều and Luong Quan plains. Continuing on, the Sông Hương (Hương River) flows to the north-east to Huế and passes the resting place of the Nguyễn emperors. The river continues, passing Hen islet and various villages, crossing the Sinh junction (capital of ancient Châu Hóa) before emptying into the Tam Giang lagoon. From Bằng Lãng to the Thuan An estuary, the river is 30 km long and runs very slowly (as the river level is not much above sea level). The river darkens as it winds along the foot of Ngọc Trản mountain, where there is a deep abyss.
The 105m Ngự Bình mountain has a strikingly symmetrical figure. On both sides of the Even Mount (Bang Son) are two small mounts, Ta Bat Son (left mount) and Huu Bat Son (right mount). After observing that Bang Son resembled a screen, the Nguyễn Dynasty decided to build up Huế, which became known as their "Forbidden Purple City". Emperor Gia Long approved the design of geomancers which chose this mount as a front altar of the imposing and solid defending wall system, and renamed it Ngự Bình.