Pha Din Pass: Red silk cotton flowers are in full bloom on Pha Din Pass, located in Phong Lai commune, Thuan Chau district, Son La province. This pass is recognized as one of the four great mountain passes in the northwestern region of the country. Spanning 32 kilometers, Pha Din Pass serves as the gateway to the northwestern mountainous province of Dien Bien.

According to Vietnam News Agency, the pass reaches its highest peak at 1,648 meters above sea level, making it an ideal location for cultivating spring flowers. In March, the fiery petals of red silk cotton flowers illuminate the pass, enhancing the misty and striking landscape of the northwestern mountainous area.