Containing the sacred fire and the Palladium, an effigy of Athena (Minerva) believed to have been brought by Aeneas from Troy, this ancient temple was built in imitation of a primitive round hut, its hearth fire symbolizing the perpetuity of the Roman State. It was not a true temple in that its space was not inaugurated, nor did it contain an image of Vesta, the goddess of the household hearth. As the handmaidens of Vesta, the principal duty of the six Vestals was never to allow the flame to be extinguished, an arduous task in a building with a vent in the roof. There also was danger that the temple, itself, might catch fire, which it sometimes did. It was destroyed in the fire of Nero in AD 64, which reached this point in the Forum. The last time it burned, in AD 191, the temple was restored by Julia Domna, the wife of Septimius Severus. Once a year, on June 15, the ashes of the tended fire were ritually thrown into the Tiber.
This view from the Palatine Hill give a better view. Completely stripped of its marble in the mid-sixteenth century, a section of the temple was reconstructed in 1930.
A templum is a space defined by the taking of auspices or for conducting some form of augury or other sacred activity (Varro, De Lingua Latina, VII.6ff). The Temple of Vesta was not inaugurated and so, properly speaking, is not a temple but an aedes sacra or "sacred building," which was a shrine or sanctuary where a god resides.
