The border between two lands is more than a line; it reinforces the hopes and fears of the nations that share it. After the Berlin Wall fell in 1989, a vision of a borderless world emerged: one less afraid, that would rely on technology, not fences, to assert sovereignty. It didn't happen. Instead, there's been a profusion of physical boundaries. The six maps here illustrate the methods – both old-fashioned and high tech – nations use to build walls in an anxious world.

1. The Colonial Border: the Strait of Gibraltar The southernmost cities of Spain actually lie in North Africa, the last vestiges of a colonial age in which Morocco was a province of France and Spain. The port of Ceuta sits a mere 8 miles from the European mainland across the Strait of Gibraltar; Melilla is some 150 miles east. In 1995, Spain and six other European nations agreed to erase internal borders. Within months, illegal immigrants began seeping into Spain's North African outposts. To stem the flow, Spain and the EU funded the construction of walls around both cities. Melilla's wall, completed in 1998, sealed its 6-mile border with parallel 10-foot fences topped with barbed wire. Ninety miles of underground cable connect spotlights, noise and movement sensors, and video cameras to a central control booth. A similar system in Ceuta was completed in 2001.

2. The Cold War Border: the Korean DMZ Created along the 38th Parallel in 1953 when South Korea, North Korea, the US and UN officials signed the cease-fire agreement that halted the Korean War, the Demilitarized Zone is anything but. Two and a half miles wide and 156 miles long, the DMZ is mostly barren land harboring some 1 million land mines; it's bound by concrete antitank walls and crowned with concertina wire. President Clinton called it "the scariest place in the world." The US provides South Korea with sophisticated intelligence-gathering technology, such as heat-seeking scopes used at guard posts and recon from satellites and aerial surveillance.

3. The Pointless Border: the Ferghana Valley The historical heart of Central Asia – it was part of the Silk Road – the Ferghana Valley is a fertile plain shared by Kyrgyzstan, Tajikistan, and Uzbekistan. After a civil war in Tajikistan and the discovery that the Ferghana's precipitous canyons sheltered Taliban-aligned Islamic fundamentalists, Uzbekistan lined its frontiers with thousands of land mines and heavily armed guards, an effort that has succeeded mostly in killing scores of innocent villagers. International opinion holds that what little hope exists for the ravaged economies of these republics lies in cooperative economic policies and free trade. Uzbekistan's response has been to add more mines and guns along the border.

4. The Homeland Border: US and Mexico The two primary objectives at the 1,989-mile US-Mexico border are largely at odds: expediting some $636 million in legal cargo per day and stanching the flow of illegal goods and immigrants. Since 9/11, Customs and Border Protection has employed a variety of Bond-like technologies. Detection devices include handheld radiation pagers, the $1.3 million Vacis gamma-ray machine, and MobileSearch radiation portals for vehicles (Wired 10.11). To speed legitimate traffic, CBP has launched the Sentri system: Frequent border crossers in El Paso, Texas, and in Otay Mesa and San Ysidro, California, affix transponders to their cars that beam digital photo IDs to inspectors who confirm the identity of drivers before waving them through.

5. The Contested Border: Kashmir India and Pakistan have been fighting over Kashmir since 1947. The last full-scale conflict ended in 1971, when the current 450-mile "line of control" was established. In the Karakoram Pass, in northern Kashmir, some 10,000 soldiers face off across a front line that ranges from 9,000 to 22,000 feet in elevation, making this the highest-altitude conflict ever. And one of the most pointless: The area is poor in natural resources and tactically insignificant. International observers say continued enmity between the countries amounts to a grudge match. That doesn't mean it's without portent. In 1999, Pakistani-sponsored mujahideen seized a ridge and nearly sparked a nuclear war. Several thousand soldiers have died over the past two decades, mostly from high-altitude sickness, avalanches, or falls.

6. The Containment Border: the Gaza Strip and the West Bank Israel's policy toward the occupied territories is one of strict containment. It controls access to the Gaza Strip through checkpoints along the lattice of roads, walls, and fences throughout the area. Along the West Bank, Israel is constructing what it calls a security fence – though the description is a gross understatement. If fully built, the enclosure will consist of a network of barriers, including 10-foot walls topped with barbed wire and guard towers and employing motion detectors and video cameras. An 80-mile section is due to be completed in July. Plans call for the 230-mile barrier to follow the so-called green line marking Israel's border with the West Bank. In reality, the wall already juts well into the area in order to keep Jewish settlements within Israeli territory.

The West Bank itself is fragmented into discrete sections of Israeli and Palestinian control connected by tunnels and bridges and defined with barriers. In his essay "The Politics of Verticality," architect Eyal Weizman notes that this is one of the few borders to fully embrace the vertical dimension: Israel, for instance, asserts its control of both the aquifer below the occupied territories and the airspace above them. The most extreme example of vertical borders was Clinton's 2000 Camp David proposal that the Temple Mount be divided horizontally, giving Palestinians sovereignty over the mosque on the top half and Israel sovereignty beneath the pavement, which includes the Wailing Wall.