Steven Saylor began publishing his Roma Sub Rosa mystery series in 1991 with Roman Blood, a novel centered on one of Cicero’s actual legal cases — the defense of Sextus Roscius against a charge of parricide — and has continued through more than a dozen novels, each using a historical crime or legal proceeding as the vehicle for an exploration of late Republican Rome. The series’ detective, Gordianus the Finder, operates as an investigator for hire in a society that had no professional police force, appearing at the margins of the major political events of the period and providing a ground-level perspective on the world that the official historical record’s focus on senators and generals does not supply.

Gaius Suetonius Tranquillus wrote the Lives of the Twelve Caesars — biographies of Julius Caesar through Domitian — probably in the early second century AD, and the work has been read continuously ever since, generating controversy about its reliability that has not diminished its influence by the slightest degree. Suetonius was the secretary of the emperor Hadrian before being dismissed, apparently for inappropriate familiarity with the empress, and he had access to the imperial archives during his service. Whether he actually used the archives, and how judiciously, is a question classical scholars continue to disagree about.

Tacitus is the most important historian the Roman world produced and one of the most important historians in any tradition. He is also, unmistakably, a man writing under conditions that shaped his account in ways he could not always control and occasionally did not try to. He was a senator who served the emperors he despised, a man who had survived Domitian’s reign by keeping his head down and who never entirely forgave himself for it, and who wrote history as an act of witness and accusation that the dead and the living were equally subject to. His prose style — compressed, ironic, capable of saying in a subordinate clause what lesser writers would require a paragraph — has influenced historical writing ever since and is the primary source for everything popular culture believes about Tiberius, Caligula, Nero, and their courts.

In the autumn of 9 AD, three Roman legions — the Seventeenth, Eighteenth, and Nineteenth — were destroyed in the forests of Germania over the course of three days. The commander, Publius Quinctilius Varus, fell on his own sword. Approximately twenty thousand soldiers died. The eagle standards of all three legions were captured — the most significant military humiliation in Roman history, measured by what it did to the Roman strategic imagination. Augustus, reportedly, wandered through his palace for months afterward crying out for Varus to give him back his legions. Whether or not he actually said this, the story captures the psychological weight of what had happened.

Frontinus, the Roman senator appointed curator aquarum — superintendent of waters — in 97 AD, opened his report on Rome’s water supply with a sentence that has been quoted many times since: compare, if you will, the idle pyramids, or the useless though famous works of the Greeks, with these many indispensable structures. The arrogance is characteristic, and the comparison is not entirely fair. But the underlying point is not wrong. Rome’s aqueduct system was among the most impressive engineering achievements of the ancient world, and it was, unlike the pyramids, entirely functional — designed to do something specific, doing it at scale, and doing it for centuries.

The arch is not a Roman invention. The Babylonians built arches. The Egyptians built arches. The Etruscans used the arch centuries before Rome became a significant power. What Rome did with the arch was different in kind from what any previous civilization had achieved: it deployed the arch at a scale and consistency that transformed the built environment of three continents, in forms — the vault, the barrel vault, the groin vault, the dome — that enabled the massive public spaces that define Roman architecture, and it left behind enough surviving examples that the arch became synonymous with Rome in the European architectural imagination.

In 186 BC, the Roman Senate issued the senatus consultum de Bacchanalibus — the decree concerning the Bacchic rites — one of the most extensive surviving Roman legal documents and the record of what the Roman state did when it decided that a religious movement had gotten out of hand. The decree restricted the Bacchic associations throughout Italy, required their leaders to present themselves for investigation, set numerical limits on how many people could participate in the rites, and prohibited Bacchic priests from holding funds or conducting initiations without specific Senate authorization. Thousands of people were prosecuted; the sources describe executions in numbers that suggest a systematic repression rather than individual criminal cases. The Bacchanalia, as the Roman sources describe it, was the first large-scale persecution of a religious movement in Roman history.

The kingdoms that replaced Roman administration in the western provinces were not anti-Roman. This is the most important correction to the standard narrative of Rome’s fall, and it matters because the standard narrative — civilized Rome overwhelmed by barbarous outsiders — is both factually wrong and interpretively misleading. The Visigothic kingdom in Spain, the Ostrogothic kingdom in Italy, the Burgundian kingdom in the Rhône valley, the Frankish kingdom in Gaul — these were not negations of Rome. They were, in varying degrees, continuations of Rome under different management, sustained by Roman administrative forms, legitimated by Roman imperial titles, and often governed by rulers who had spent significant portions of their careers in Roman service and who regarded Roman civilization as the culture they had inherited rather than the culture they had defeated.

The Circus Maximus was the largest sports venue the ancient world ever built, capable of holding somewhere between 150,000 and 250,000 spectators — the ancient sources give figures that seem implausibly large but are not entirely implausible given the site’s archaeology. For comparison, the Colosseum held perhaps 50,000 to 80,000. The Circus was Rome’s dominant entertainment venue, chariot racing was Rome’s dominant spectator sport, and the passion Romans invested in the circus factions — the Blues, Greens, Reds, and Whites — was of an intensity that modern sports tribalism only partially approximates. In Constantinople, a dispute between circus factions contributed to a riot that killed tens of thousands of people and nearly ended Justinian’s reign. This is the world that chariot racing inhabited.

The Cloaca Maxima — the Great Drain — is among the oldest continuously functioning pieces of Roman infrastructure. Built initially in the sixth century BC to drain the marshy valley between the Capitoline and Palatine hills that would become the Roman Forum, it has been carrying water to the Tiber for over 2,600 years. Tourists floating on the Tiber can still see its outlet — a rounded arch of tufa stone nearly four meters high, set into the river embankment near the Forum Boarium — and the drain itself, though substantially rebuilt and extended over centuries, remains active as part of Rome’s modern sewer and stormwater system. It is one of the oldest pieces of civil engineering in continuous use anywhere in the world.