Antioch on the Orontes — modern Antakya in southern Turkey near the Syrian border — was the third city of the Roman Empire and the capital of its eastern operations. After Rome and Alexandria, no city in the Mediterranean world was larger or more strategically important. It was the administrative center for the Syrian provinces, the supply base for Rome’s eastern wars, the commercial hub connecting the Mediterranean trade network to the silk and spice routes of Asia, and an early center of Christian organization so significant that the word Christian — Christianoi — was first used there. The city that matters to understanding Rome’s eastern empire is Antioch, and it is among the most underrepresented in the popular historical imagination.