Earlier buildings According to the
Liber pontificalis,
Pope Mark established a basilica in a place called
ad Pallacinas in 336. This first church was built atop preexisting,
pre-Constantinian structures of unknown date or function, but excavations in the mid-20th century revealed a surviving ancient
Roman mosaic with
acanthus vine-scroll ornamentation underneath the present-day basilica's right aisle. Pope Mark's first church incorporated walls from this earlier structure, and featured a new colonnade,
opus sectile pavements, and
frescoed walls, of which a small fragment depicting several horses survives underneath the present-day basilica. It is likely that the previous ancient Roman structure was initially a residence owned by Pope Mark, who then gifted the property to a Christian congregation within the first few months of his papacy.
Present-day basilica According to the
Liber pontificalis,
Pope Gregory IV saw the ruinous state of the second church and decided to have it demolished in 833 to rebuild the basilica now seen today. The new church's floorplan also aligns with the prior churches, with two aisles flanking a nave that terminates in an apse. The floor consists of large blocks of tufa that were likely part of the
Servian walls. Gregory IV's unique contributions to this rebuilding was the monumental
apse mosaic, the annular
crypt, and the
clerestory. The apse mosaic is the best surviving element of the Gregory IV's resconstruction in 833. It depicts
Jesus in the center with Pope Mark,
St. Agapetus, and
St. Agnes to his left and
St. Feliccissimus, Gregory IV, and St. Mark the Evangelist to his right. All seven figures stand against a solid golden backdrop standing atop pedestals with inscriptions identifying the figures. Below the figures, twelve lambs representing the
Twelve Tribes of Israel, lead out of
Bethlehem and
Jerusalem and surround the
Lamb of God. On the apsidal arch,
St. Peter and
St. Paul stand beneath the roundels of Christ and the
Four Evangelists. The
Latin dedicatory inscription running along the bottom of the apse mosaic reads:
English translation: The huge supports of the apse, which shine like
Solomon's temple beneath the stars, rests on a solid foundation. These things, O Mark, the pope with the distinguished name of Gregory IV has made for you and in your own honor. And you pray that God may grant him a long life on earth and after death lead him to the stars of heaven. The choice to position Mark the Evangelist in the composition in the place traditionally reserved for St. Peter appears to be an intentional subversion of established apse mosaics depicting groups of saints with the donor pope. Art historian Claudia Bolgia suggests that the translation of
Mark's relics from
Alexandria to
St. Mark's Basilica in
Venice in 830–31 had an influence on Pope Gregory IV's decision to depict himself in relationship to this particular evangelist. Furthermore, the inclusion of Sts. Agapetus and Feliccissimus may refer to Gregory IV having recently sent their relics to a
Bavarian monastery. Therefore, the apse mosaic evokes the spiritual presence of these saints, despite their relics physically existing outside of Rome and, therefore, the immediate jurisdiction of the
Holy See. Further changes were made to the church throughout the 12th century, with the addition of a
Romanesque campanile above the southern end of the nave, sculptural work around the main southern portal, and a new
ciborium above the high
altar. From 1465–70,
Pope Paul II renovated the church's façade according to the
Renaissance taste, with a two-storied
portico and
loggia, using marbles taken from the
Colosseum and the
Theater of Marcellus. It was at this time that the church was incorporated into the
Palazzo Venezia complex, and the clerestory windows were enlarged and ornamented with
Gothic tracery, a common feature of
Quattrocento Roman architecture. During the early modern period, the church's interior underwent two major redecoration campaigns in the
Baroque style. From 1654–57,
Niccolò Sagredo commissioned
Orazio Torriani to redecorate the colonnade with regularized
Ionic capitals and white-washed shafts. Then, from 1732–54, Cardinal
Angelo Maria Quirini commissioned
Filippo Barigioni to redesign the high altar and choir stalls. In 1843, Gregory IV's annular crypt, which had been closed in 1474 under
Cardinal Marco Barbo, was rediscovered. Excavations in 1947–50 revealed the foundations and remnants of the earlier churchs, as well as a large cypress chest in the crypt that contained the relics of Pope Mark,
St. Abdon and St. Sennen. ==Cardinal priests==