President Trump made his banner campaign promise to build a wall along the nation’s entire 2,000-mile border with Mexico, suggesting that he would shut down the government if Congress doesn’t fund the project.

While Trump has been criticized for the idea, and derided for his vow to make Mexico pay for it, he is far from the first modern-day leader to want to wall off his country. Since the Berlin Wall fell in 1989, dozens of countries have gone on a massive barrier-building campaign, with the number of border walls soaring from 15 then to about 70 now. Many countries have decided to build walls in the wake of the Arab Spring and the Syrian refugee crisis, while others are trying to counter terrorists or fear Russian invasions.