Introduction to the underground palace: The underground palace under the church is a huge tomb. Here, more than 140 popes, as well as the German Emperor Otto II and Queen Christina of Sweden, are buried. The sarcophagus lid is inscribed With their names, dozens of ever-burning lamps in the underground palace are kept on day and night. There is no sense of gloom or terror, leaving visitors with the impression of tranquility and tranquility.