Maps. Any study of Roman history, particularly topics such as foreign policy, international relations, and multiculturalism, must begin from the assumption that the Romans had only a rudimentary understanding of where they were in relation to others. Their knowledge of geography—the distances between two points, the bend and flow of rivers, the compass directions among regions—was as limited as one might expect for a culture without access to aerial observation. The Romans did try to make maps of their empire, but none survive; what little is known about them suggests that they were terribly inaccurate. Nonetheless, some were posted in prominent places. As early as 174 B.C.E. the Roman conqueror of Sardinia put up a map of the island in the Temple of Mater Matuta to illustrate his accomplishments. In the reign of Augustus, the general Agrippa had...