Basins, plains, and highlands often provide a country with excellent agricultural land and easy transport options. The Mississippi Basin, North China Plain, North European Plain, Brazilian highlands, and Argentina’s Rio de la Plata lowlands are among the world’s major agricultural areas. They also provide corridors for invaders, as with the North European Plain, which provides easy access to Russia’s western border.

Many borders form naturally along mountain ranges, rivers, coastlines, deserts, and jungles. Others are laid down artificially by invading colonizers. Natural borders do a reasonable job of keeping some distance between competing groups, allowing them to evolve separately. Artificial borders often cut across ethnic or linguistic lines, forcing incompatible groups to live together while separating related ones. This can lead to conflicts, especially in the Middle East and Africa, where colonial powers divided regions into countries with little thought for the inhabitants.

Examples of artificial borders include the Sykes-Picot Line that divides Syria from Jordan and Iraq, the Durand Line between Afghanistan and Pakistan (which the Pashtun peoples ignore with impunity), the Spanish-Portuguese carve-up of South America, the US-Mexican border, and the Demilitarized Zone between North Korea and South Korea.