There are lots of wall in the world built in different ages. Many of them were made to protect Nations by invasions... other instead were made to divide people.
The Great Wall of China was built from 375 to 1644 and it's 21.196 km kong; it made people feel safe and it was useful beacuse China was able to stop conquerors. The same reasons urged the Roman imperor to build the Hadrian's Wall in Britain to stem the Scottish tribes.
The Berlin Wall was built in 1882, after the Second World War, to divide the German capital in two factions. The east one was under control by Russia and the west one was controlled by France, Us and Great Britain. Families were separeted for years and about 100 people died because they attempted to climb over the wall. Those seven years were so difficult for the citizens and in 1889 they tore down the hated divider.
We have to learn from history, we don't have to forget what happens in the past! Repeating errors shows that humanity couldn't improve its mentality. Young people that are the future of the world, must respect the planet and other populations because everyone must have a decent life and should have its rights respected!