Yen Tu (Chinese: 安子山

Yen Tu (Chinese: 安子山, Yen Tu Son) is a mountain range stretching across the three provinces of Quang Ninh, Bac Giang, and Hai Duong and is also the name of the highest mountain in the range. This is a mountain range associated with the Tran Dynasty in Vietnamese history as well as with the Truc Lam Zen sect. Yen Tu range belongs to the Dong Trieu arc, one of the four main mountain arcs in the Northeast region of Vietnam. The mountain range has a terrain that gradually decreases from east to west, with an average height of over 600 m above sea level; the highest point is Yen Tu peak (1,068 m) and the lowest point is the Con Son - Kiep Bac area (200–238 m), near Luc Dau Giang. The southern slope (also known as the East Yen Tu slope) mainly belongs to Quang Ninh province and a small part belongs to Hai Duong province, while the northern slope (also known as the West Yen Tu slope) belongs to Bac Giang province. Historically, Yen Tu has always been one of the Buddhist centers of the country, associated with many ancient architectures, built through different historical periods (Ly, Tran, Le, Nguyen). In 1294, after King Tran Nhan Tong abdicated the throne to his son Tran Thuyen (King Tran Anh Tong) and became the Supreme Emperor, he became a Buddhist monk at Vu Lam Palace, Ninh Binh. In 1299, he came to Yen Tu, took the dharma name Huong Van Dai Dau Da or Truc Lam Dai Dau Da, and attracted many disciples[6][7]. Here, he built a system of pagodas, hermitages, and towers and founded the Truc Lam Zen sect, a Buddhist Zen sect with Vietnamese cultural identity that exists to this day.