This is a great question. As you probably know the Vestal Virgins were an important priesthood in Rome. They were responsible for the sacred fire of Vesta as well as a few other things, such as making the molsa salsa, which was used for sacrifices. If a Vestal Virgin was found to have transgressed the gods by unchastity or a breech in their responsibilities, the punishment was great. Let me give you a few bullet points:
- The Vestal Virgin was dressed in funeral garments.
- She was then bound hand and foot and placed in a closed litter.
- She was brought to the Colline Gate to undergo her horrible fate.
- She was escorted by the Pontifex Maximus to an underground chamber.
- She was given some basics things for life.
- Finally she was buried alive, and her lover was beaten to death (in the case of unchastity).
We can read about these things in Plutarch Questions, 96 and Dionysius of Halicarnassus 2.67.4.