Alexandria was not a Roman city. It was a Greek city under Roman administration, founded by Alexander the Great in 331 BC and designed from its inception as a world capital — a city that would connect the Mediterranean world to Egypt and, through Egypt, to the trade routes of the East. By the time Rome absorbed it as part of Egypt following Cleopatra’s death in 30 BC, Alexandria was already three centuries old, the second-largest city in the Mediterranean after Rome itself, and possessed of institutions — the Library, the Museum, the great lighthouse — that Rome had nothing to rival. The Romans did not conquer Alexandria so much as inherit it, and the inheritance was complicated.

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.

Caesarea Maritima was built by Herod the Great on a site with no natural harbor, no fresh water source, and no existing urban infrastructure, over a period of approximately twelve years ending around 10 BC, and it became the capital of the Roman province of Judaea and one of the most important cities on the eastern Mediterranean coast. The feat of urban creation involved harbor engineering that modern marine archaeologists have called the most ambitious building project in the ancient world: an artificial harbor of roughly 100,000 square meters created by sinking enormous concrete blocks into water sixty meters deep, using hydraulic concrete — the pozzolanic technology that gave Roman harbor structures their extraordinary durability — in its most ambitious application anywhere in the empire. The harbor blocks, two thousand years later, still lie beneath the Mediterranean, structurally recognizable and studied by diving archaeologists who find in them evidence of Roman engineering at its most technically extraordinary.

Carthage must be destroyed. The phrase — Carthago delenda est — was reportedly repeated by Cato the Elder at the end of every Senate speech he gave, regardless of the speech’s actual subject, in the years before the Third Punic War. It is probably apocryphal, or at least exaggerated, but it captures something true about the Roman relationship with Carthage: a fear and hostility so intense that it could only be resolved by elimination, and a political culture prepared to act on that resolution against a city that had been, by the 140s BC, effectively defanged by the terms of its previous defeat.

Ephesus was the most important city in the Roman province of Asia — which meant it was one of the most important cities in the world. At its imperial peak in the second century AD, its population may have reached 200,000 to 500,000 people, making it one of the three or four largest urban centers in the Roman Empire after Rome itself and Alexandria. It sat at the western terminus of the major trade routes from the Anatolian interior and the eastern Mediterranean, on a harbor that connected it to the Aegean sea lanes, and it possessed in the Temple of Artemis one of the seven wonders of the ancient world. What the site preserves today — the most extensively excavated and partially reconstructed ancient city in the world — is an archaeological window into Roman urban life of a quality available nowhere else.

The Romans did not found London because they needed a city there. They founded it because they needed a crossing point on the Thames, and the crossing point became a city because trade and administration followed the military logic that had chosen the site. The settlement that grew up at the first substantial tidal ford on the Thames — approximately where London Bridge stands today — was called Londinium, and within a century of its founding it had become the administrative capital of the Roman province of Britannia and one of the most important commercial cities in the northwestern empire. Britain was at the edge of the known world; Londinium was a world city transplanted to the edge.

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.

Palmyra occupied a position in the Syrian desert that geography had made irreplaceable and that commerce had made extraordinarily wealthy. An oasis city sitting at the crossing of the major caravan routes between the Mediterranean coast and Mesopotamia — between the Roman west and the Parthian and Sassanid east — it controlled the tolls and services that long-distance trade required and accumulated wealth that its extraordinary ruins still convey despite two millennia of decay and, most recently, deliberate destruction by forces who understood, in their way, the symbolic weight of what they were attacking.

On the morning of August 24, 79 AD — though some scholars now argue for a date in October based on pomegranate seeds and autumn clothing found in the excavations — Mount Vesuvius began its eruption. By the following morning, the city of Pompeii was buried under four to six meters of volcanic ash and pumice. Approximately eleven thousand people lived there. Somewhere between two and three thousand did not escape. The volcano that killed them preserved them, and what it preserved has told us more about ordinary Roman life than any literary source.