Vestal Virgin

The Vestals or Vestal Virgins were a group of priestesses of the Roman goddess Vesta, in Ancient Rome. 
The Vestals were a part of the College of Pontiffs ("Collegium Pontificum"). They were responsible for looking after the "sacred fire" of Vesta, which was not allowed to go out. Unlike most other women in Roman society, the Vestals were forbidden to marry or bear children, and took a vow of chastity when they joined the priesthood, which lasted for a minimum of 30 years.
They were daughters chosen before puberty from a number of suitable candidates, from two living parents who both had to be free-born residents (not slaves or freed slaves) of Rome. Before the 3rd century BC, candidates for Vestal priesthoods had to be of patrician birth. Membership was opened to plebeians in the 3rd century BC.
They retired when their term of service ended after 30 years. Vestals who retired, typically in their late 30's to early 40s, were allowed to marry, but were often too old to bear children.
Vestal Virgins who broke their vow of chastity, were ritually killed by being buried alive.