Beneath the historic streets of Pula lies Zerostrasse, a network of tunnels that were built during World War I to shelter the city’s residents from air raids. These cool, echoing corridors once served as a wartime refuge, and today they invite visitors to explore a hidden world below the Roman amphitheater. Not just a passage through history, Zerostrasse also connects to Pula Castle—visitors can take an elevator from the tunnels straight up to the hilltop fortress, where stunning panoramic views of the city await.