Your challenge is to make the following possible:
In WW2, it's the Soviets who liberate Italy and they make it a Warsaw Pact Communist country.
However after a few talks between the Western Allies and the Soviets, a decision is made:
The Vatican, in the middle of Rome will be a part of the geopolitical West. The Pope and the Catholic Church will stay there.
The Italians build the Iron Curtain around the Vatican which will be known as "The Roman Wall."
Transport of people and goods between Western countries and the Vatican is made possible by pre-determined transit routes through Communist Italy.