Ostia was the famed port of Rome located just 26 km from the empire’s capital. The site provides some useful comparisons and contrasts with Pompeii, allowing us to explore the role of streets in the use of urban space in more depth. Both cities are in Italy, the center of the Roman Empire, and both are among the most thoroughly excavated and best published ancient cities in the Mediterranean. Nonetheless, Ostia differs in several signifi cant respects from its sister city in Campania. The Romans constructed Ostia for a singular purpose, to facilitate the transportation and mercantile needs of Rome, unlike Pompeii, which grew over time, meeting a variety of needs. Because of its importance to Rome, the emperors lavished more attention and funds on the city than any other besides Rome itself. Ostia was also a larger and more densely occupied city than Pompeii. Finally, Ostia did not meet a catastrophic end, but rather grew, functioned, and was slowly abandoned over a period of more than a millennium. The continuous use of the site presents some chronological diffi culties when trying to examine the street network and the buildings that lined it. By choosing to examine the city at its height at the end of the Severan era, the fi rst third of the third century CE, however, and including only those buildings known to have been standing and occupied at that time, some of the chronological problems recede, making it possible to compare some of the details of the street network of Ostia with that of Pompeii.