Early 18th-century depiction of the dedication of a Vestal, by Alessandro Marchesini
Terms of service
The Vestals were committed to the priesthood before puberty (when 6-10 years old) and sworn to celibacy for a period of 30 years. These 30 years were divided in turn into decade-long periods during which Vestals were respectively students, servants, and teachers. Afterwards, they were retired and replaced by a new inductee. Once retired, a former Vestal was given a pension and allowed to marry. The Pontifex Maximus, acting as the father of the bride, would typically arrange a marriage with a suitable Roman nobleman. A marriage to a former Vestal was highly honored, and – more importantly in ancient Rome – thought to bring good luck … as well as a comfortable pension.
To get admittance into the order, a girl had to be free of physical and mental defects, have two living parents and be a daughter of a free-born resident of Rome. From at least the mid-Republican era, the pontifex maximus chose Vestals between their sixth and tenth year, by lot from a group of twenty high-born candidates at a gathering of their families and other Roman citizens. Originally, the girl had to be of patrician birth, but membership was opened to plebeians as it became difficult to find patricians willing to commit their daughters to 30 years as a Vestal, and then ultimately even to the daughters of freedmen for the same reason. 
The choosing ceremony was known as a captio (capture). Once a girl was chosen to be a Vestal, the pontifex pointed to her and led her away from her parents with the words, “I take you, Amata, to be a Vestal priestess, who will carry out sacred rites which it is the law for a Vestal priestess to perform on behalf of the Roman people, on the same terms as her who was a Vestal ‘on the best terms'” (thus, with all the entitlements of a Vestal). As soon as she entered the atrium of Vesta’s temple, she was under the goddess’s service and protection.
To replace a Vestal who had died, candidates would be presented in the quarters of the chief Vestal for the selection of the most virtuous. Unlike normal inductees, these candidates did not have to be prepubescents, nor even virgins (they could be young widows or even divorcees, though that was frowned upon and thought unlucky), though they were rarely older than the deceased Vestal they were replacing. Tacitus (Annals ii.30,86) recounts how Gaius Fonteius Agrippa and Domitius Pollio offered their daughters as Vestal candidates in AD 19 to fill such a vacant position. Equally matched, Pollio’s daughter was chosen only because Agrippa had been recently divorced. The pontifex maximus (Tiberius) “consoled” the failed candidate with a dowry of 1 million sesterces.
House of the Vestals and Temple of Vesta from the Palatine
Their tasks included the maintenance of the fire sacred to Vesta, the goddess of the hearth and home, collecting water from a sacred spring, preparation of food used in rituals and caring for sacred objects in the temple’s sanctuary. By maintaining Vesta’s sacred fire, from which anyone could receive fire for household use, they functioned as “surrogate housekeepers”, in a religious sense, for all of Rome. Their sacred fire was treated, in Imperial times, as the emperor’s household fire.
The Vestals were put in charge of keeping safe the wills and testaments of various people such as Caesar and Mark Antony. In addition, the Vestals also guarded some sacred objects, including the Palladium, and made a special kind of flour called mola salsa which was sprinkled on all public offerings to a god.
The dignities accorded to the Vestals were significant.
in an era when religion was rich in pageantry, the presence of the College of Vestal Virgins was required in numerous public ceremonies and wherever they went, they were transported in a carpentum, a covered two-wheeled carriage, preceded by a lictor, and had the right-of-way;
at public games and performances they had a reserved place of honor;
unlike most Roman women, they were not subject to the patria potestas and so were free to own property, make a will, and vote;
they gave evidence without the customary oath, their word being trusted without question;
they were, on account of their incorruptible character, entrusted with important wills and state documents, like public treaties;
their person was sacrosanct: death was the penalty for injuring their person and their escorts protected anyone from assault;
they could free condemned prisoners and slaves by touching them – if a person who was sentenced to death saw a Vestal on his way to the execution, he was automatically pardoned.
they participated in throwing the ritual straw figures called Argei into the Tiber on May 15.
Allowing the sacred fire of Vesta to die out, suggesting that the goddess had withdrawn her protection from the city, was a serious offence and was punishable by scourging. The chastity of the Vestals was considered to have a direct bearing on the health of the Roman state. When they entered the collegium, they left behind the authority of their fathers and became daughters of the state. Any sexual relationship with a citizen was therefore considered to be incest and an act of treason. The punishment for violating the oath of celibacy was to be buried alive in the Campus Sceleratus or “Evil Field” (an underground chamber near the Colline Gate) with a few days of food and water.
Ancient tradition required that an unchaste Vestal be buried alive within the city, that being the only way to kill her without spilling her blood, which was forbidden. However, this practice contradicted the Roman law that no person might be buried within the city. To solve this problem, the Romans buried the offending priestess with a nominal quantity of food and other provisions, not to prolong her punishment, but so that the Vestal would not technically die in the city, but instead descend into a “habitable room”. Moreover, she would die willingly. Cases of unchastity and its punishment were rare. The Vestal Tuccia was accused of fornication, but she carried water in a sieve to prove her chastity.
O Vesta, if I have always brought pure hands to your secret services, make it so now that with this sieve I shall be able to draw water from the Tiber and bring it to Your temple.
Because a Vestal’s virginity was thought to be directly correlated to the sacred burning of the fire, if the fire were extinguished it might be assumed that either the Vestal had acted wrongly or that the vestal had simply neglected her duties. The final decision was the responsibility of the Pontifex Maximus, or the head of the pontifical college, as opposed to a judicial body. While the Order of the Vestals was in existence for over one thousand years there are only ten recorded convictions for unchastity and these trials all took place at times of political crisis for the Roman state. It has been suggested that Vestals were used as scapegoats in times of great crisis.
The earliest Vestals at Alba Longa were said to have been whipped to death for having sex. The Roman king Tarquinius Priscus instituted the punishment of live burial, which he inflicted on the priestess Pinaria. But whipping with rods sometimes preceded the immuration as was done to Urbinia in 471 BC.
Suspicions first arose against Minucia through an improper love of dress and the evidence of a slave. She was found guilty of unchastity and buried alive. Similarly Postumia, who though innocent according to Livy was tried for unchastity with suspicions being aroused through her immodest attire and less than maidenly manner. Postumia was sternly warned “to leave her sports, taunts and merry conceits.” Aemilia, Licinia, and Martia were executed after being denounced by the servant of a barbarian horseman. A few Vestals were acquitted. Some cleared themselves through ordeals. The paramour of a guilty Vestal was whipped to death in the Forum Boarium or on the Comitium.