South Vietnam is divided into four relatively distinct physiographic regions--the Mekong Delta, the coastal plain, the Annamite Mountains, and the forested plain. The Mekong Delta, an extensive and fertile lowland centered on the Mekong River, covers roughly the southern quarter of the country. This region is essentially a marshy flat land well suited for rice growing and is recognized as one of Asia’s richest agricultural areas. South Vietnam’s second physiographic region, the coastal plain, is similar to the Mekong Delta in that it is predominantly flat and generally well suited for rice growing. Properly known as the coastal lowland, this region extends from the country’s northern border to the Mekong Delta. Its width is never constant, being defined on the west by the rugged Annamite Mountains--the region which dominates the northern two thirds of South Vietnam. The jungle-covered mountains, whose highest elevations measure over 8,000 feet, stand in sharp contrast to the low and flat coastal plain. The eastern slopes of the mountains normally rise from the lowlands at a distance of five or 10 miles from the sea. At several points along the coast, however, the emerald mountains crowd to the water’s edge, dividing the coastal plain into compartments and creating a seascape breathtaking in its beauty. At other locations the mountain chain recedes from the coast, allowing the lowlands to extend inland as far as 40 miles. An extensive upland plateau sprawls over the central portion of South Vietnam’s mountain region. This important subregion, known as the Central Highlands, possesses relatively fertile soil and has great potential for agricultural development. The highest elevations in the Annamite chain are recorded south of the Central Highlands. From heights of 6,000 to 7,000 feet, the mountains dissolve southward into the forested plain, a hilly transition zone which forms a strip between the Mekong lowlands and the southernmost mountains.