Located 320km northwest of Hanoi, Son La town is often used as a half-way overnight stop on the way to Dien Bien Phu. There is not much to remark the town except a prison built in 1908 by the French colonialists to incarcerate the Vietnamese political criminals. However, from Son La to Dien Bien Phu you will see lots of minority villages – Black Thai, white Thai, H'mong, and Muong – some close to the road. Black Thai women wear black sarongs, and tightfitting blouses with rows of silver or metal buttons down the front attached tightly to the neck. The blouses are usually bright green, blue, or purple. A woman coils her hair in a topknot, covering it with a black turban embroidered with multicolored thread. After marriage, Black Thai women wear a silver hairpin. Some 800, 000 Black Thai and White Thai (white-bloused Thai people) live in the Northwest.