Quotes of the Day

The Great Wall of China, the mother of barriers, isn't holding up so well. Rapacious builders are swiping its venerable stones for apartment complexes and pigsties, historians question the tale of its creation and China's pioneer astronaut Yang Liwei declared on his return to earth last year that he couldn't see it from space. But around the world, countries are building similar structures to foil the modern version of barbarians—terrorists—or simply would-be immigrants.

Israel's ongoing construction of a 700-km security barrier in the West Bank—a $1.4 billion combination of ditches, towers, concrete walls and barbed-wire fences—has sparked an international furor. Palestinians protest that the serpentine fence is an illegal annexation of lands for Israelis that also manages to divide villages and farmers from their fields. So far, 200 km have been erected.

The 3,200-km border between the United States and Mexico is one of the most breached international boundaries in the world. There's fencing along 130 km, and Washington wants to add 23 km of backup fences near the Pacific Ocean.

Thailand's 500-km border with Malaysia is a porous conduit for drugs, weapons and people. In the mid-1990s the government of Malaysia built an $18 million concrete wall along 20 km of the border; last month Thai Prime Minister Thaksin Shinawatra proposed extending the fence to counter Islamic separatists carrying out attacks in southern Thailand.

India is in a fence-building boom. New Delhi says insurgents in northeastern India take advantage of the porous border with Bangladesh; so by 2007, it intends to fence in the entire 4,894-km border except for rivers. India also has barriers on the Pakistan border and is pushing ahead with a fence along the 767-km Line of Control in the disputed region of Jammu and Kashmir.

Bill Clinton called the Demilitarized Zone (DMZ) that divides North and South Korea the "scariest place on earth." The 248-km de facto border is also one of the world's most impenetrable barriers, but some gaps are starting to appear. Since the late 1990s, both sides have been removing mines to construct cross-border links. The first road through the DMZ opened near the east coast last year, and work is proceeding on rail and highway links that would connect Seoul with the North Korean border city of Kaesong.

• Austin Ramzy
• Around the world, walls are going up on porous borders to keep modern-day barbarians at bay