Phu Sa Phin (also known as Ta Xua Peak) is the highest peak in the Ta Xua mountain range, reaching an altitude of 2,865m - 2,868m above sea level. This mountain serves as a rugged natural boundary between Hang Chu commune, Bac Yen district, Son La province and Tram Tau district, Yen Bai province. It is considered one of the most pristine and captivating trekking routes in the Northwest region thanks to its unique primary ecosystem. Highlights at Phu Sa Phin: - The Enchanting Moss Forest: The ancient forest of cypress, chestnut, and rhododendron trees, hundreds of years old, is covered in layers of deep green, damp moss from root to tip, creating a mysterious atmosphere. - The Dinosaur's Backbone: A treacherous trail running along a narrow, steep, and windy mountain ridge offers a thrilling experience for adventure enthusiasts. - Cloud-hunting paradise: At an altitude of nearly 2,900m, visitors can admire the vast sea of ​​white clouds swirling below on ideal weather days. To reach the summit of Phu Sa Phin, trekking groups usually choose one of the following two routes: - The Son La route (towards Hang Chu/Xim Vang): Shorter climbing distance (about 4km on the first day), moderate slope, and picturesque mossy forest scenery, reducing danger and making it very suitable for first-time climbers. - The Yen Bai route (towards Ban Cong, Tram Tau): Steep, rugged terrain, windy, challenging, and requires endurance. Many people choose a combined route: climbing up from the Hang Chu direction and descending towards Tram Tau to fully experience the scenery on both sides. The ideal time to visit is from October to the following April. This is the dry season in the Northwest, characterized by sunny, dry weather, fresh air, and the highest probability of successfully witnessing the "cloud-hunting" phenomenon. During March and April, rhododendrons bloom profusely across the cliffs surrounding the mountain peak. You must be in good physical condition due to the relatively long distance (approximately 22-28 km). Always hire a local porter to ensure you don't get lost and to stay safe from sudden weather changes in the deep forest.