BOUNDARIES AND BORDERS
Elsewhere in the world
To keep in: East Germans.
Length: 103 miles (surrounding West Berlin).
The Berlin Wall was far more than a physical barrier separating East and West Germany. As the physical embodiment of the Iron Curtain, the wall quickly became the central symbol of the ongoing Cold War.
Erected almost overnight by the Soviets and East Germans, the Wall was meant to stem a tide of migration from the East to the West. Its concrete barriers, guards, electric fences and armed checkpoints slowed the flow, but almost 200 people were killed while attempting to defect; thousands more made it across or were stopped in the process. The wall finally was torn down in 1990.
To keep out: Troops from each side.
Length: 151 miles.
Described by former President Clinton as "the scariest place on Earth," the Demilitarized Zone (DMZ) that divides the two Koreas is a Cold War legacy that has yet to thaw. Established under the 1953 armistice that put the Korean War on hold, the DMZ bristles with land mines, towers, razor wire and nearly 2 million soldiers from the two Koreas. More than 37,000 U.S. troops are stationed in South Korea. Although effectively chilling the armed conflict that once threatened to provoke a world war, the frontier is one of the world's touchiest: If North Korean troops cross the DMZ in force, the United States is, under a 1954 agreement, automatically committed to war.
Fortified: the 20th century.
To keep out: Illegal immigrants and workers from Latin America.
Length: 2,000 miles.
An extension of the natural barrier created by the Rio Grande River, the border between the United States and Mexico is the front line of a massive economic and cultural struggle. Mexican workers and families, seeking the relatively plentiful and rewarding jobs inside the United States, risk confrontation with U.S. Border Patrol agents and the INS as they cross the border by the hundreds of thousands. A greatly beefed-up U.S. security presence along the border has decreased the numbers of immigrants trying to make the increasingly difficult crossing, and fatalities have decreased in recent years. But the crossing still takes a harsh human toll; every year, hundreds of immigrants die in the scorching desert or drown while crossing the river.
GREAT WALL OF CHINA
Built: Around 220 B.C.
To keep out: Invaders from the north.
Length: roughly 4,500 miles.
Knitted together from a rugged patchwork of far smaller improvised barriers and built over the course of a millennium, the Great Wall of China remains one of humanity's most ambitious feats of engineering. Historians estimate that building the Great Wall cost more than a million lives and the equivalent of hundreds of billions of U.S. dollars. Although pricey, the wall kept northern invaders at bay with varying and still-debated amounts of success until the Mongol conquests in the 13th and 14th centuries.
Source: Christian Science Monitor