Gate of Hercules are old city gates that were erected in the time of the Middle Ages judging by rough technique in their production. Although several stones were apparently taken from older Roman buildings. The name of the Gate of Hercules is derived from a carving above the entrance that reminded Pula residents of the mythical Greek- Roman hero holding a battle club. Today it is barely visible due to natural erosion. The inscription next to bas- relief is from a Roman origin and mentions two Roman officials, Lucius Calpurnius Piso and Gaius Cassius Longinus. These name are important in the history of Pula since these were the officials that were entrusted by the Roman Senate to found a Roman colony on a site of modern day Pula between 47 BC and 44 BC.
Lucy Cassy Longin was the brother of Gaius Cassia Longin, one of Caesar's murderers. The fact that Cassie Longin has played such an important role encourages discussions about the exact year of the beginning of Pula. Many believe that it is impossible for him to have this role as a brother of Caesar's assassin, and they believe that it is more probable to start the development of Pula in the years preceding the Caesar's assassination.