Sacred fire of Vesta
The Sacred fire of Vesta, the Roman goddess of the hearth, was a symbol of the hearth and the home. The maintenance of the sacred fire, the communal hearth of Rome, in the Temple of Vesta (Aedes Vesta), was the primary responsibility of the Vestal Virgins. The fire was renewed on the first day of March. Vesta and her sacred fire were considered tightly bound to the fortunes of the city. Failure to "show proper respect for Vesta and the fire was punishable by death".
The fire of Vesta was closely linked with the well-being of Rome. Within Vesta's circular temple in the Roman Forum, the sacred fire of the Roman state burned. The temple existed from pre-republican times until 394, when the fire was extinguished by order of Theodosius and the Vestal Virgins disbanded.
It is reported that the temple occasionally caught fire from the magnitude of the sacred fire. The current temple (somewhat restored in the 20th century) dates from 191 AD, when Julia Domna, wife of the emperor Septimius Severus, ordered a thorough rebuilding.
Analysis
There was a single sentence of speculation by electrical engineer Nikola Tesla concerning the fire of Vesta as representing electrical plasma, in his article "A fairy tale of electricity" (published September 9, 1915), where he claims "it was very plausible [...] that the vestal fires of the Romans were electrical." [1]. Plausible, he states, though the evidence that it was indeed the case is sparse. Tesla's was well read and may have seen historical evidence that led him to make this fairy tale suggestions (eg., the amber Phenomena was well known in Roman times).
Some believe that no actual historical evidence for this and many historians are in agreement that the fire of Vesta was an ordinary flame.