Vietnam extends approximately 331,688 square km (128,066 sq mi) in area. The area of the country running along its international boundaries is 4,639 km (2,883 mi). The topography consists of hills and densely forested mountains, with level land covering no more than 20%. Mountains account for 40% of the area, with smaller hills accounting for 40% and tropical forests 42%. The northern part of the country consists mostly of highlands and the Red River Delta. Phan Xi Pang, located in Lao Cai province, is the highest mountain in Vietnam at 3,143 m (10,312 ft). The south is divided into coastal lowlands, Annamite Chain peaks, extensive forests, and poor soil. Comprising 5 relatively flat plateaus of basalt soil spread over the provinces of Dac Lac, Gia Lai, and Kon Tom, the highlands account for 16% of the country’s arable land and 22% of its total forested land. Before 1975, North Vietnam had maintained that the Central Highlands and the Giai Truong Son were strategic areas of paramount importance, essential to the domination not only of South Vietnam but also of the southern part of Indochina. Since 1975, the highlands have provided an area in which to relocate people from the densely populated lowlands.
The delta of the Red River , is a flat, triangular region of 3,000 square kilometers, is smaller but more intensely developed and more densely populated than the Mekong River Delta. Once an inlet of the Gulf of Tonkin, it has been filled in by the enormous alluvial deposits of the rivers over a period of millennia, and it advances one hundred meters into the Gulf annually. The ancestral home of the ethnic Vietnamese, the delta accounted for almost 70 % of the agriculture and 80 % of the industry of North Vietnam before 1975. The Mekong delta, covering about 40,000 square kilometers, is a low-level plain not more than three meters above sea level at any point and criss-crossed by a maze of canals and rivers. So much sediment is carried by the Mekong’s various branches and tributaries that the delta advances sixty to eighty meters into the sea every year. An official Vietnamese source estimates the amount of sediment deposited annually to be about 1 billion cubic meters, or nearly 13 times the amount deposited by the Red River. About 10,000 square kilometers of the delta are under rice cultivation, making the area one of the major rice-growing regions of the world. The southern tip, known as the Ca Mau Peninsula, or Mui Bai Bung, is covered by dense jungle and mangrove swamps