Photo Gallery Today's High-Tech Barriers
The Spanish exclaves of Ceuta and Melilla, remnants of the colonial era, are located in Northern Africa, but they are securely sealed off from the rest of the continent. African refugees looking for a way out continue to try and storm the stronghold. Those who have enough money can even swoop in via helicopter.
More than 1,000 kilometers (700 miles) of wall and fence along the United States border has proven unsuccessful in keeping out Mexican smugglers, traffickers and illegal immigrants. Washington has given up on the wall, but the state of Arizona, known for strong anti-immigration measures, wants to persist with plans to continue building on its own.
The 760 kilometers (472 miles) or fortifications that criss-cross the Holy Land are not expected to disappear anytime soon. The Israeli security barrier is intended to deter terrorists, but Palestinians see the structure as a land-grab effort. Israel has continued construction, ignoring the established cease-fire line and exacerbating the Mideast crisis.
The barrier dividing North and South Korea is technically a cease-fire line marking the division between two entities that are, officially, still at war. Watchtowers, guns, wire traps and helmeted guards on both sides make the dividing line one of the most dangerous in the world. But tourists still flock to the South Korean side of the wall.
The civil war is over and Northern Ireland is, theoretically, at peace. But tensions remain, as do the so-called "Peace Walls" which have shaped the cityscape of Belfast for 40 years. Not only are the walls still standing, many residents openly support their continued existence.