Propiska in the Soviet Union

Propiska was something you needed if you wanted to live in or visit a city or town in the Soviet Union (a group of countries that used to be together in Europe and Asia). It was like an official stamp that said you were allowed to be in the city. It was hard to get propiska because the government had to keep track of who was going in and out of the cities. Without propiska, you had to stay in the same city forever!