After the great fire of 64 CE in Rome which destroyed many multi-level mud brick buildings, mostly apartment dwellings. When Rome began rebuilding it self, they built flat top concrete vaults in to the space between floors. Concrete being a fire-resistant material.
July 19th 64 CE
- Great Fire of Rome – Wikipedia
The Torches of Nero, by Henryk Siemiradzki. According to Tacitus Nero targeted Christians as those responsible for the fire. The Great Fire of Rome was an urban fire that started on the night between 18 and 19 July in the year 64 AD. It caused widespread devastation, before being brought under control after six days.
- Nero’s Rome burns – Jul 18, 64 – HISTORY.com
The great fire of Rome breaks out and destroys much of the city on this day in the year 64. Despite the well-known stories, there is no evidence that the Roman emperor, Nero, either started the fire or played the fiddle while it burned. Still, he did use the disaster to further his political agenda.
- H. V. Canter • Conflagrations in Ancient Rome — Classical Journal 27 …
In reading the Roman historians one comes upon numerous references to fires and losses by fire in ancient Rome,1 not only such as are to be expected in the ordinary course of an ancient city’s life but conflagrations of very serious consequences, which devastated great areas and involved the partial or total loss of houses, tenements, markets, granaries, storehouses, and splendid public buildings.
- Golden House of Nero | palace, Rome, Italy | Britannica.com
Golden House of Nero, Latin Domus Aurea , palace in ancient Rome that was constructed by the emperor Nero between ad 65 and 68, after the great fire of 64 (an occasion the emperor used to expropriate an area of more than 200 acres [81 hectares] of land in the centre of the city).