Why did Nikita Khrushchev order the construction of the Berlin Wall?
I think your answer refers to the Berlin blockade instigated by Stalin in 1948.
The building of the Berlin Wall was for the same reason, namely preventing the exodus of East Germans from East to West Berlin then to West Germany. It was built in 1961.
It's destruction in 1989 was one of the most powerful symbols of the collapse of communism.