On the Adriatic coast, became an important city during the late Roman Empire. According to legend it was evangelized by St Mark, but the beginnings of the Church cannot be traced beyond the 3rd cent. In 381 its bishop, Valerian, appears as metropolitan of the Churches in the area and under him and his successor, Chromatius, Aquileia was a centre of learning. The floor of the basilica (rebuilt in the 11th cent.) is covered with early 4th-cent. mosaics.