Donald Trump has taken to Twitter in recent days to defend the building of his southern border wall after it emerged millions of dollars has been spent on rebuilding only a tiny section of it.
What his election promise to “build it big and make Mexico pay” has done is divide opinion in the US.
But it will be by no means the only physical barrier dividing countries and communities.
Their number has grown sharply from just seven at the end of World War Two to an estimated 80 now.
We’ve been to visit three fences and walls in Europe the people who live behind them