It has been almost 27 years since the fall of Berlin Wall, a symbol of the division between the capitalist West and communist East. Now, new walls, fences and barriers are going up across the world, separating nations and states from one another.
According to research by the University of Quebec in Canada, about 40 countries have built border fences dividing them from their neighbours since 1989.
As Europe continues to grapple with a refugee crisis caused mainly by the civil war in Syria, barriers are going up across the continent. Austria, Hungary, Bulgaria, Macedonia and several other Balkan countries are all attempting to fortify their borders.
But these structures are only just beginning to be built. Here are some examples of longstanding walls, which often symbolise longstanding ethnic, religious and political divisions:
Israel's West Bank separation wall
The West Bank separation wall was built in 2002 on the orders of former Israeli Prime Minister Ariel Sharon. Palestinians protested the wall’s route, 85 percent of which runs east of the Green Line set by the United Nations demarcating Palestine from Israel.
Egypt's steel fence along the Gaza Strip
After Israel pulled out of the Gaza Strip in 2005 Egypt built an 11 km long steel fence separating its territory from the Palestinian enclave. The wall, which Egypt says is aimed at preventing smuggling, stretches 18 metres below the surface of the land it is built on in order to deter tunnel-building.
Two border fences separating Spanish enclaves from Morocco
Spain has two fenced enclaves in North Africa surrounded by Morocco – Ceuta and Melilla. It justifies the fences by saying they are intended to protect Spain from illegal migrants.
The Korean Demilitarized Zone
In 1953, after the end of the Korean War, a demilitarised zone, or DMZ, was established between South and North Korea. Barbed-wire fences and fortifications were erected in this area to prevent people from crossing from one side to the other and in preparation for any future conflict.
Northern Ireland's Peace Walls
The Peace Walls were built to separate Catholic and Protestant communities living in Northern Ireland. The aim was to stop violence between the mostly Protestant Loyalists who want the province to remain part of the UK and mostly Catholic Irish Republicans who want it to join the Republic of Ireland.
US-Mexico border fence
The construction of a fence along the US border with Mexico was started after a surge in violence, drug trafficking and illegal immigration. It was completed in 2011, but the public debate around it hasn't ended. Recently, presumptive Republican presidential nominee Donald Trump breathed new life into the issue by pledging to build a wall along the border.
A country surrounded by walls
Pope Francis has been one of the biggest critics of Trump’s plan to build a wall across the US border with Mexico, saying he was "not Christian" for expressing such views. However, the Pope leads the Vatican, a state surrounded by large walls.