Imagine waking up one morning to find a wall blocking your street. You cannot visit your best friend on the other side. That is exactly what happened in Berlin, Germany, in 1961. After World War II, the winning countries split Germany into two nations. East Germany was controlled by the Soviet Union. West Germany was allied with the United States and other Western countries. The city of Berlin sat inside East Germany but was also divided. In 1961, East German leaders built a concrete wall right through the city. Families were separated overnight. Guards watched the wall with guns. Anyone who tried to cross could be shot. For 28 years, the wall stood. Then in November 1989, something remarkable happened. East Germany's government grew weak. Huge crowds gathered at the wall. The guards stepped aside. People climbed the wall, and strangers on both sides hugged and celebrated. Less than a year later, on October 3, 1990, East and West Germany officially became one country again. The reunification was celebrated with fireworks, music, and tears of joy. Today, parts of the wall are displayed in museums around the world as reminders of what division looks like.