On the night of August 24, 410, the Roman Princess Galla Placidia was waiting for the end of the world. Although she left no record of her feelings on that fateful evening, we can recreate the scene as the 20-year-old noblewoman wandered the imperial palace complex on the Palatine Hill in the heart of the ancient city. Her surroundings exuded all the ancient splendor and confidence of the Roman Empire, the greatest the Western world had ever seen. The floors and walls of the palace were a kaleidoscope of colored marble embedded with gold and precious gems. Silver fountains burbled in the courtyards. Antique statues of military heroes and illustrious Caesars jostled with artwork and trophies brought back by the conquering legions from far-flung corners of the Mediterranean.

This was Rome, a megalopolis where glittering avenues, monuments and arches littered the landscape. A census listed 46,602 multistory tenement buildings, 1,790 palatial villas, 856 bathhouses, 28 libraries and 1,352 fountains, not to mention ten aqueducts and a sewage system. However, the city had fallen on hard times since the golden age of great emperors, like Trajan, Hadrian and Marcus Aurelius, more than two centuries earlier. Its cosmopolitan population had shrunk from one million to 600,000, and lawlessness reigned in many streets; the gladiatorial spectacles in the Colosseum were shut down in 404, leaving the chariot races as the main public entertainment. But even in decay there was no rival to Roma Aeterna, the Eternal City, Caput Mundi, the Head of the World, invincible and invulnerable … or so its citizens had believed for some 800 years.

In 410, Rome’s situation was teetering toward the unimaginable. Camped in the countryside around its titanic, marble-sheathed defensive walls was a vast army of some 100,000 warriors led by the king of the Visigoths (western Goths) named Alaric, who had marched from the Balkans under the banner of a black crow. The enemy army besieged Rome for three months, blocking its 12 gates and all transport on the Tiber River.

With her classical education, Placidia would have recalled Homer’s haunting description of the Trojan army in the Iliad. The enemy campfires were so numerous, he wrote, they blazed like the stars in the night sky.

The Emperor Honorius, Placidia’s half-brother, had long since abandoned Rome to its fate. Of the imperial family, only the princess had remained, offering her regal support to the Senate as it worked to stave off disaster. Now, the city was on its knees. The population was starving. Bodies piled up in the streets. Rumors of cannibalism spread. Disease ran rampant. Many pagans blamed the Christians: Placidia’s own father, Theodosius the Great, had ordered dozens of pagan temples in the city closed, snuffed out the sacred flames of the Vestal Virgins and banned the sacrifices to the ancient gods who had protected Rome from enemy incursion for eight centuries.

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For Romans, it was the beginning of the end. But for Placidia, it was just one more twist in an astonishing life saga that could have inspired a subplot of “Game of Thrones.” After the sack, the pampered and beautiful princess would be taken from her gilded palace as a prisoner of the Visigoths. Four years later, Placidia shocked Romans by marrying one of her captors. Then, by age 26, she was back in Italy, re-inventing herself to rule as the last empress of the Western Roman Empire.

And yet, she has been treated mercilessly by historians, who have either vilified or ignored her for most of the last 1,500 years. This has left her today all but forgotten, even though the final decades of the Western world’s most enduring empire cannot be understood without her.