"In geography, a plain is a flat, sweeping landmass that generally does not change much in elevation. Plains occur as lowlands along valleys or on the ...
[Read more]
doorsteps of mountains, as coastal plains, and as plateaus or uplands.
In a valley, a plain is enclosed on two sides, but in other cases a plain may be delineated by a complete or partial ring of hills, by mountains, or by cliffs. Where a geological region contains more than one plain, they may be connected by a pass (sometimes termed a gap). Coastal plains would mostly rise from sea level until they run into elevated features such as mountains or plateaus." - (en.wikipedia.org 05.10.2020)