In July 64 CE a fire that began among the shops around the Circus Maximus burned for some nine days, destroying ten of Rome's fourteen administrative districts and leaving only four untouched. In the rebuilding, the emperor Nero imposed new rules: streets were widened, building heights were capped, party walls were required, and porticoes of fire-resistant stone were mandated along the new frontages, with water kept accessible for firefighting. The state also funded the clearance of rubble and offered incentives to speed reconstruction. The disaster cleared ground for Nero's vast palace complex, the Domus Aurea.
It produced one of the first systematic sets of fire-and-building regulations applied to an entire city, establishing the principle that urban form could be reshaped through public rules on materials, heights and street width.