the Republic, in the preferred medium of bronze. Similarly stern and forceful heads are seen on coins of the Late Republic, and in the Imperial period coins as well as busts sent around the Empire to be placed in the basilicas of provincial cities were the main visual form of imperial propaganda; even Londinium had a near-colossal statue of Nero, though far smaller than the 30-metre-high Colossus of Nero in Rome, now lost. The Romans did not generally attempt to compete with free-standing Greek works of heroic exploits from history or mythology, but from early on produced historical works in relief, culminating in the great Roman triumphal columns with continuous narrative reliefs winding around them, of which those commemorating Trajan (CE 113) and Marcus Aurelius (by 193) survive in Rome, where the Ara Pacis ("Altar of Peace", 13 BCE) represents the official Greco-Roman style at its most classical and refined. Among other major examples are the earlier re-used reliefs on the Arch of Constantine and the base of the Column of Antoninus Pius (161), Campana reliefs were cheaper pottery versions of marble reliefs and the taste for relief was from the imperial period expanded to the sarcophagus. All forms of luxury small sculpture continued to be patronized, and quality could be extremely high, as in the silver Warren Cup, glass Lycurgus Cup, and large cameos like the Gemma Augustea, Gonzaga Cameo and the "Great Cameo of France". For a much wider section of the population, moulded relief decoration of pottery vessels and small figurines were produced in great quantity and often considerable quality. After moving through a late 2nd-century "baroque" phase, in the 3rd century, Roman art largely abandoned, or simply became unable to produce, sculpture in the classical tradition, a change whose causes remain much discussed. Even the most important imperial monuments now showed stumpy, large-eyed figures in a harsh frontal style, in simple compositions emphasizing power at the expense of grace. The contrast is famously illustrated in the Arch of Constantine of 315 in Rome, which combines sections in the new style with roundels in the earlier full Greco-Roman style taken from elsewhere, and the Four Tetrarchs (c. 305) from the new capital of Constantinople, now in Venice. Ernst Kitzinger found in both monuments the same "stubby proportions, angular movements, an ordering of parts through symmetry and repetition and a rendering of features and drapery folds through incisions