What was built by East Germany in 1961 to prevent citizens from escaping to the West?

The Berlin Wall was constructed in 1961 by East Germany as a physical barrier to stop the mass emigration of its citizens to West Berlin and, by extension, to other parts of West Germany. This dramatic action arose from the increasing number of East Germans who were fleeing to the West for better economic opportunities, political freedom, and living conditions.

The Berlin Wall symbolized the broader conflict of the Cold War, representing the division between the communist Eastern Bloc and the democratic Western nations. Its construction was intended to signify the commitment of the East German government to keep its citizens within its borders, thereby preventing a "brain drain" and maintaining the regime's control.

Other choices, such as the Iron Curtain, refer to the ideological boundary between the Soviet bloc and the West but do not represent a physical barrier like the Berlin Wall. The Maginot Line was a French defensive fortification built along the German border, and the Great Wall of China is an ancient structure unrelated to the context of Cold War divisions in Europe. Thus, the Berlin Wall is the correct answer, as it directly pertains to the question of stopping East Germans from seeking freedom in the West.