Low flat land is often referred to as a plain. Plains are typically characterized by gently rolling hills and broad valleys with relatively low elevations. They can be found in many different parts of the world and can vary in size from small, localized areas to vast stretches of land that span multiple countries. Plains are typically formed by the deposition of sediment over a long period of time, often from the erosion of surrounding mountains or the accumulation of material from rivers and glaciers. They are also commonly found in coastal areas, where they are formed by the gradual accumulation of sediment from the ocean.