The Via Purifico is a prison located in the lower sections of Bevelle. There is no way to revisit this area after the team travels through the area.
The Via Purifico is made up of two sections - the prison section that Yuna, Kimahri, Auron and Lulu explore and the underwater section which Tidus, Wakka and Rikku explore. Check out the walkthrough and strategy guide section for additional details: