Pope Pontian
Pontian served as pope mostly during the reign of Roman Emperor Severus, generally considered a peaceful period for Christians, but died during the reign of Maximinus Thrax.  Maximinus Thrax did not tolerate Christians and pursued them violently.  He arrested Pontian and Hippolytus and sent them to the mines in Sardinia where they died soon after.  Pontian's body was returned to Rome a short time later and they were buried in the catacombs of Callistus on the Appian Way.  Catacombs were underground chambers where many Christians lived, died and were buried.