Walls of the world aim to keep unwanted foreigners out, hold prosperity in

United States and Mexico

Much of the United States' border with Mexico — 650 miles — has a steel and concrete barrier. Building the fence began in 2006 during the George W. Bush administration. Cameras, sensors, floodlights, drones and an increase in law enforcement agents along the frontier have been part of an American strategy to keep out economic migrants and fight drug smuggling.

Immigration remains one of the controversial topics in US politics even as President Barack Obama has moved to offer more favorable legal arrangements for many in the country illegally. However, Obama has also dedicated more resources to shoring up the border, where security personnel have risen to over 21,000. Meanwhile, the share of undocumented migrants from Mexico has shrunk in recent years, with numbers having peaked in 2007.

Meanwhile, the issue has become one of the core debates in the Republican presidential race. Leading candidate Donald Trump has called for ramped up wall-building, which costs at least $3 million per mile in urban areas, but up to four times more in rural desert stretches. The total bill for finishing off the wall for the entire border has been estimated at $20 billion.

European Union

Anti-immigrant sentiment in Europe is rising, amid the recent influx of hundreds of thousands from war-torn countries such as Syria, Afghanistan and Somalia.

On its 109-mile Serbian border, Hungary has rushed to finish a double fence topped with razor wire. The Hungarian government says the 13-foot barrier will stem a huge flow of refugees fleeing conflicts mainly in the Middle East. At a cost of over $100 million, hundreds of soldiers aim to complete the project by year’s end, as 1,000 people cross the border each day. 

In 2012, Greece began building a barbed wire fence on its border with Turkey near the Evros River to prevent entry of the EU. Meanwhile, Bulgaria’s government is putting up a new fence to prevent undocumented immigration from Turkey. 

Middle East

The controversial separation barrier built in the West Bank and along the Green Line separating Israel from Palestinian territory seized during the 1967 Middle East war winds its way through almost 400 miles of hilly, disputed terrain. With a combination of steel fences, concrete walls and barbed wire, Israel has said it aims to keep fighters out, while critics say it creates a de facto border and a land grab.

Construction began in 2002 and the barrier includes sophisticated intrusion detection equipment designed to stop Palestinians from crossing into Israel. Many Israelis call it the “security fence,” while it’s often known in Arabic as the “Apartheid Wall.” The territory encompassed by the barrier includes almost 10 percent of West Bank land, and around 85 percent of Israeli settlers. Many Palestinians are forced to cope with a complicated checkpoint regime in order to access farms and jobs, both within the West Bank and Israel proper.

Weekly protests against the wall are held by Palestinian and international activists in several villages such as Nabi Saleh and Bil’in. With the Israeli Supreme Court ruling in some cases against the military’s chosen route, the intricate system of trenches, roadblocks and dirt mounds has damaged the Palestinian economy and freedom of movement, but also accompanied a significant decrease in attacks within Israel. Regardless, thousands of Palestinian laborers continue to cross illegally every day to work inside Israel.

There are other walls in the region. On the edge of the Gaza Strip, Israel has another highly fortified fence. Egypt has strengthened fences along its own border with Gaza. In 2013, the Israeli government largely completed a fence along the Egyptian border to keep out migrants and smugglers seeking to enter from the Sinai Peninsula. Besides the fence between the West Bank and Jordan, Israel is also now building a fence to keep fighters out along an 18-mile stretch of its border with Jordan in the far south of the country near the Red Sea. Along the border with Lebanon and Syria, Israel has also built complex security barriers.

Arabian Peninsula

The Saudi government is constructing a security barrier on its long, porous 1,100-mile frontier with Yemen as that country has been riven by civil war and military intervention. Running from the Red Sea to Oman, the border is marked by sandbags, concrete pipeline and electronic detection systems.

The southern border has become the scene of increased violence, but efforts on the northern border have have also recently intensified, with a 600-mile “Great Wall” marking the Iraqi frontier. With the threat of infiltration by the Islamic State in Iraq and the Levant (ISIL), a system of sand berms, concertina fences, movement sensors and reconnaissance stations has been created out in the desert.

To the east, a 120-mile border fence separates Iraq from Kuwait, with the original UN-sanctioned intention to prevent invasion. Electric fences and dirt berms have recently been buttressed by an iron barrier. Elsewhere in the region, the United Arab Emirates is building a fence on its border with Oman to control the flow of migrants and drugs.

Morocco

Rippled berms run across a swath of Western Sahara terrain highly disputed by Morocco, Algeria and Mauritania. The 1,700 miles of barriers built in the 1980’s are made of sand, barbed wire, bunkers and landmines. The Moroccan government quickly put up six successive walls during that period, building upon territory claimed by Rabat as its forces moved south, taking land from the Polisario rebels fighting for an independent nation.

Now, the wall demarcates the Moroccan-occupied “Southern Provinces” from the Polisario-controlled areas to the south and east, known as the Free Zone or Sahrawi Arab Democratic republic. Dozens of Moroccan troops are based at observation posts every three miles. In addition, radars are positioned along the barrier, ready to target Polisario forces, many of whom are based in refugee camps inside Algeria’s Tindouf province.

On the other side of Morocco, EU member Spain has fenced off its two Mediterranean exclaves Ceuta and Melilla to stop smuggling and illegal entry of migrants. However, Morocco does not recognize Spanish sovereignty over these areas on the African continent, and thus has objected to the construction of the 20-foot fences.

South Asia

Extending 2,500 miles across the vast expanse of curved border between India and Bangladesh, the New Delhi government continues to erect a concrete and barbed wire wall. With border guards from the Indian Border Security Forces and watchtowers alongside paddy fields, India aims to keep out illegal entrants and stop human trafficking. 

Violence along the border has resulted in some 1,000 people being killed during the last decade, as security worries often drive Indian troops to open fire on Bangladeshi migrants. Many villages have been divided by the wall, although forces on the border are reportedly more lenient about crossing during religious festivals. Another fence along India’s border with Myanmar hopes to seal that 1,000-mile border to keep out currency smugglers and drug traffickers.

Moreover, in the disputed territory of Kashmir, along the Line of Control with Pakistan, India has constructed over 300 miles of fencing. The barrier includes motion sensors, thermal imaging and alarms. Between two rows of fences and concertina wire are landmines. Pakistan has criticized the project, while Indian military officials say it has improved security.

Meanwhile, on the Iran-Pakistan border, Tehran has been building a 435-mile stretch of fencing through the Balochistan region. Communities divided by the wall have criticized its construction, though Iran argues that it helps restrict illegal activities and the flow of black market goods.

North and South Korea

The demilitarized zone has cut across the 38th parallel separating North and South Korea since a 1953 armistice agreement ended fighting in the Korean War. The fences are lined with barbed wire to stop infiltration and defection going both ways across a demarcation boundary splitting the DMZ in half.

With the Koreas still technically in a state of war, border tensions have periodically flared up. Military clashes have resulted in the deaths of hundreds of South Koreans, in addition to more than 50 Americans. Pyongyang-backed atttempts to burrow below the border have been largely unsuccessful.

Southern Africa

The fence separating Botswana from Zimbabwe runs over 300 miles, with a six-foot high barbed wire fence that was a originally intended to keep out cattle infected with foot and mouth disease. Zimbabwe’s government argues that the barrier is merely intended to prevent Zimbabwean people crossing illegally from a country with economic turmoil to a more prosperous place. But the fence is scarcely patrolled, and gaps created by rivers offer porous crossings for people and animals alike.

Two apartheid-era fences were built on South Africa’s borders with Zimbabwe and Mozambique. The former was erected in 1984, with an electric core and two rows of fencing totaling some 15 feet in width. The “Snake of Fire” shocked anyone who approached, and significant parts of the fence remain. On the Mozambique border, a new 100-mile fence was begun in 2012 to deter poaching adjacent to Kruger Park.

Central Asia

Uzbekistan has four different prominent security barriers on its borders, built either by itself or its neighbors. On the Kyrgyz border, Uzbekistan is building a controversial fence through the Ferghana Valley. The Tashkent government says the barrier is for security purposes. Reportedly to stop drug smuggling, Kazakhstan constructed a 28-mile fence on its border with Uzbekistan.

And along Uzbekistan’s heavily militarized southern border with Afghanistan, a 130-mile electrified barbed-wire fence attempts to prevent the spread of violence from the ongoing Afghan conflict. Turkmenistan, in 2001, began a 1,000-mile border fence along its northern border with Uzbekistan to hamper migration flows and human trafficking.