Berlin Mayor Michael Mueller has urged US President Donald Trump "not to go down the road of isolation" with his planned border wall with Mexico.
Mr Mueller warned such divides cause "slavery and pain" and would "destroy the lives of millions".
The German city was divided by the Berlin Wall from 1961 to 1989.
Mr Mueller's statement came as Mr Trump and Mexican President Enrique Pena Nieto agreed to "work out their differences" over the issue.
The planned wall was one of Mr Trump's key election campaign pledges, but it has cast a shadow over the US's relationship with its neighbour.
Mr Pena Nieto has repeatedly stated that Mexico will not pay for the wall and has condemned a US suggestion that it may impose a 20% tax on his country's imports to finance the structure.
"We Berliners know best how much suffering was caused by the division of an entire continent," Mr Mueller said in a statement, referring to Europe's "Iron Curtain".
He said the city could not "silently look on as a country sets about building a new wall".
"We cannot let our historical experience get trashed by the very people to whom we
owe much of our freedom: the Americans.
"I call on the president not to go down the road of isolation," the statement reads (in German). "Mr President, don't build this wall."
source : BBC