Rome could not feed itself. The city that consumed the products of an empire — grain from Egypt and North Africa, wine from Gaul and Spain, olive oil from the eastern Mediterranean, luxury goods from as far as India and China — sat on the Tiber sixteen kilometers from the sea, connected to the Mediterranean economy through a harbor at the river’s mouth and the logistical infrastructure that moved commodities from ships to warehouses to the city’s tables. Ostia was that infrastructure, and understanding it means understanding how an ancient city of half a million or more people solved the supply problem that has defeated urban civilizations throughout history.

The Romans mass-produced glass. This statement requires emphasis because it contradicts the common assumption that mass production is a modern phenomenon and that ancient luxury goods were necessarily handmade in small quantities by skilled artisans serving elite clients. Roman glass was made in those ways too — the cameo glass of the Portland Vase, the intricate millefiori bowls, the delicate cage cups — but alongside and beneath these luxury productions existed a glass industry of genuinely industrial character, producing standardized vessels in enormous quantities for the ordinary consumer market that constituted the overwhelming majority of Roman commercial glass transactions.

Rome and China never met. The two largest empires of the ancient world existed simultaneously — the Han dynasty and the Roman principate overlapped for roughly two centuries — and the goods they produced circulated between them across thousands of kilometers of overland and maritime routes. But no Roman diplomat reached Chang’an, and no Han envoy arrived in Rome, and what each knew of the other was filtered through so many intermediaries that the images were almost entirely mythological. Rome called China Serica, the land of silk. China called Rome Daqin, the Great Qin, imagining it as a mirror-image empire on the far western edge of the world. The distance between them was too great and the intermediary interests too profitable for direct contact to develop.