Walls are being built all over the world at a rate not seen since the end of the Cold War. Immigration, terrorism, and drug and people trafficking have largely contributed to the revival of walls.
A look at some of these walls and where they are being built:
A 4m-high wall is being built here to block "jungle" refugee camp migrants from stowing away on trucks bound for Britain. Paid for by the British government, the wall is an extension of an existing barbed-wire fence that is already flanking the road.
A 500m razor-wire fence was built along Hungary's border with Serbia and Croatia last year, after over 400,000 refugees crossed over to get to other parts of Europe. Plans are under way to build a "massive defence system next to the existing line of defence", said Hungarian Prime Minister Viktor Orban.
Ukraine will begin building "Project Wall", a barrier on its easternmost border with Russia to fortify its porous, nearly 2,000km frontier.
Announced in 2014, the ambitious project aims to prevent Russian military intervention in Ukraine.
The "Berm", a sand wall in Western Sahara, runs for about 2,700km in harsh, uninhabited territory.
It is meant to keep out Sahrawi rebels, who want to end Moroccan presence in the Western Sahara.
Morocco erected the wall in 1975, shortly after it occupied Western Sahara.
Also known as the "Apartheid Wall", the Israeli-West Bank barrier runs for 700km.
Israel says it is an anti-terrorist measure but Palestinians say it is aimed at racial segregation. Built in 2000, the wall has been effective in reducing the number of suicide bombings carried out from the West Bank, says Israel.
The wall resulted in reduced freedoms, loss of land and difficulty in accessing public services and water for the Palestinians.
Turkey is sealing its border with Syria with a 900km wall to stop the influx of Syrian refugees fleeing the war-torn country and also Islamic State in Iraq and Syria (ISIS) fighters.
It has already built 200km of the wall and will finish the rest within five months.
Saudi Arabia began planning for a barrier in 2006 after sectarian violence broke out in Iraq.
But it was not until 2014, when the ISIS threat intensified, that it started constructing the wall, which will be about 900km, and run along its isolated northern desert border.
A combination of a multilayered fence and ditch, the border will also be fortified with 78 watchtowers, night-vision and radar cameras, and eight command centres.
This article was first published in The Straits Times on Oct 4, 2016, along with the Special Report Insecurity barriers: More countries putting up walls and fences to keep others out