The interior contains the mausoleum of Pope Celestine V.
It numbers among its chambers the Gothic hall of Giovanni Pisano in which Celestine V.
Nicholas died in the palace which he had built beside Sta Maria Maggiore, and was succeeded by Celestine V.
With this organization, under the popes Zosimus, Boniface and Celestine the Roman Church came into conflict on somewhat trivial grounds, and was, on the whole, being worsted in the struggle, when the Vandal invasion of Africa took place, and for nearly a century to come the Catholic communities were subjected to very hard treatment.
About the Pelagians (whom he was not inclined to regard as heretical), gave from his own point of view an account of the disputes which had recently arisen within his patriarchate.3 While ordinarily Rome might have been expected to hold the balance between the contrasted schools of thought, as Leo was able later to do, it is not surprising that this implied appeal proved unsuccessful, for Celestine naturally resented any questioning of the Roman decision concerning the Pelagians and was jealous of the growing power of the upstart see of the Nova Roma of the East.
The successor of Gregory was Pope Celestine IX.
Henry, skilfully winning over Pisa, Genoa and the Roman Commune, isolated Tancred and intimidated Celestine III., who, on the 14th of April 1191, crowned him emperor at Rome.
He also induced Pope Celestine to publish an Epistola ad episcopos Gallorum against Cassian.
In his letters to Celestine he had laid stress on the point that the teaching he attacked was derogatory to the Godhead and so he called its champions Arians.
He helped the ineffective Celestine V.