The Istrian peninsula was conquered by the Romans in 177 BC, starting a period of Romanization. The town was elevated to colonial rank between 46-45 BC as the tenth region of the Roman Empire, under Julius Caesar. During the civil war of 42 BC of the triumvirate of Octavian, Mark Antony and Lepidus against Caesar's assassins Brutus and Cassius, the town took the side of Cassius, since the town had been founded by Cassius Longinus, brother of Cassius. After Octavian's victory, the town was demolished. It was soon rebuilt at the request of Octavian's daughter Iulia and was then called Colonia Pietas Iulia Pola Pollentia Herculanea'. The amphitheater was constructed between 27 BC - 68 AD.