Arch is the most striking feature of Roman architecture. However, the arch was not invented by the Romans, but they learned it from the Etruscans and used it by the Romans. In the construction of elevated canals and bridges, they used arches and created beautiful and practical masterpieces. In buildings like Rome and Maximus Arena, they used repeated arches and combined them with Greek columns. They arched the entrance tunnel. John ward B. Ward-Perkins said that they built the Arc de Triomphe to "commemorate the victory of the war" or "commemorate other memorable people or events, most commonly the emperor himself or the great achievements of the emperor who just died." There are still three such triumphal arches in and around Rome Square: one in memory of Titus, one in memory of septimus Severus and one in memory of Constantine the Great.