The Mekong Delta is located in South Vietnam and has been formed by deposits of sediments carried by the Mekong over centuries. It's one of the largest rivers in the world, so big in fact that it has two daily tides. The river is known locally as Sông Cửu Long (River of Nine Dragons) since it breaks into 9 separate estuaries at mouth in the South China Sea.
The area is known as the "Rice Basket" because it produces enough rice to feed the entire nation and fuel exports. While it is still a rural area, it has one of the highest population densities in Vietnam and practically the entire surface area is used for rice cultivation.