The most notable features of the interior of the church are the choir and the royal Pantheon of the kings of Navarre and later Castile and Leon.More than 30 royal family members are buried in the pantheon including Sancho II of Pamplona. The most famous tomb is that of Blanca of Navarre, wife of Sancho III of Castile, whose decorated sarcophagus is a remarkable for its frieze depicting a parade of mourners