According to historians living under the Nguyen dynasty, Phu Yen is a half-mountain and half-plain territory. It is adjacent to the South China Sea in the East, leans against the mountain in the West. It shares border with Binh Dinh province in the North (Cu Mong Pass), Khanh Hoa province in the South with the high Dai Linh Pass. The province is home to high peaks named Dai Linh and Thach Bi, large river named Da Dien. There are fortifications of Thach Linh and Phuoc Son upland used to…