Walls of the world: Barriers to movement across the globe

As President Donald Trump marked 100 days in office, he vowed to keep his campaign promise to build a wall along the border with Mexico. Despite widespread skepticism and Mexico's refusal to pay for the wall, as Trump has demanded, the U.S. government has been soliciting bids and test sections could be built as soon as this summer. Physical barriers are as old as humanity and have proved to be effective over the centuries at protecting borders. But fences can also have unwanted consequences, like destroying city neighborhoods, harming the environment and preventing innocent victims from reaching safety. Here is a look at some of the world's barriers. Some are simple, while others are massive enterprises that cost billions.

A third of the U.S.-Mexico border is already studded with an assortment of fences, but closing off the rest will be no easy task. Much of the border in Texas is blocked by the Rio Grande or other natural barriers, or runs along land owned by private citizens, many of whom oppose the wall. There also is much skepticism over whether the fence would stem drug trafficking, illegal immigration or gang violence.

Israel began construction of its 150-mile separation barrier in 2002 in response to Palestinian suicide bombings that killed more than 1,500 people. Israel says the structure is a crucial defense measure. But because it frequently juts into the occupied West Bank, the Palestinians see it as a land grab that impedes their dream of establishing an independent state.

India needed just two years to build a 340-mile fence along the disputed border area with Pakistan a decade ago. It is laced with thermal imaging devices, motion sensors and lighting systems along a mined strip of land. The Indian military calls it an "anti-infiltration obstacle system," designed to keep Pakistan-based rebels from crossing.

A United Nations-controlled buffer zone stretches 120 miles from coast to coast across the tiny island, separating the breakaway Turkish Cypriot north from the internationally recognized south. The division dates to 1974, when Turkey invaded. The frontier is rarely marked by a physical wall, with the notable exception of the capital, Nicosia, where one runs through the heart of the Old City.

The Demilitarized Zone, a Cold War vestige, was created in 1953 after the Korean War ended with an armistice. Running from coast to coast, 154-mile-long DMZ bisects the peninsula and forms the de-facto border between the Koreas. Mined on both sides, with a razor-wire fence, tank traps and hundreds of thousands of troops, the DMZ is the world's most heavily fortified border.

Hungary built fences along its southern borders with Serbia and Croatia in 2015, when thousands of migrants were passing through each day headed to Germany and other western Europe destinations. Prime Minister Viktor Orban is a staunch opponent of migration, and Hungary has been accepting only a few hundred asylum seekers a year. Human rights groups and U.N. agencies are critical of the policies.

Spain has built 20-foot layered border fences around its two North African enclaves, Ceuta and Melilla, to dissuade migrants from entering them via Morocco. The fences, along with cooperation between Spain and Morocco, have helped keep out migrants. But rights groups say Spanish and Moroccan security forces have beaten migrants caught scaling the wall.

Associated Press