Answer: The correct answer is Porta Pia. Italian forces under General Raffaele Cadorna opened fire on the Aurelian Walls near Porta Pia at dawn, creating the breach that allowed troops to enter Rome and end the temporal power of the papacy. The event marked the final act of Italian unification, reducing the Pope’s authority to the Vatican itself and beginning the long “Prisoner in the Vatican” era for Pius IX. The breach at Porta Pia remains one of the most iconic moments in modern Italian and Vatican history, symbolizing the transition from the Papal States to the modern Italian nation.