Befitting the theme of the chapel, the mosaic
decoration of the dome displays the three types of
baptism: water, blood and desire. John the Baptist pours
water over a kneeling convert. Martyrs shed their blood
as angels bring palms fronds as a crown for those who
suffer. In a crowd of people, some spread their hands in
a gesture of desire for the sacrament. In the midst
of these 'types' is the Eternal Father supported in a
Glory of clouds and angels, with the Holy Spirit dove at
his heart. On his right, Christ beckons the Apostles to
go and baptise all nations. We also see Adam and Eve
near the forbidden tree, being expelled from Paradise,
illustrating the need for baptism.
represent the four corners of the world which have
accepted baptism: Europe, Asia, Africa and America. Each
section has a woman and a representative animal: Europe
with the papal tiara - horse; Asia with a thurible - Camel; Africa - elephant; America -
In the lunettes we can view the Old
Testament prefigurations of Baptism: Moses drawing water
from a stone, and Noah praying before the rainbow after
the flood, a sign of the covenant between God and man.
There are also notable early baptisms: Christ baptizing
St. Peter, St Peter baptizes the Centurion, St. Philip
baptizing the eunuch of Queen Candace, St. Sylvester
baptizing the Emperor Constantine.
drawings (1710-1745) were by Francesco Trevisani who was one of the leading
exponents of late Baroque painting in Rome in the early
decades of the 18th century.
The mosaic work was
done under the supervision of Pietro Paolo Cristofari.
The pendentives were executed from 1724 to 1726.
Giuseppe Ottaviani did Europe and America, Liborio
Fattori did Africa, and Giovanni Brughi did Asia. The
lunettes were executed from 1737 to 1739. Nicolo Onofri
and Domenico Gossoni worked on St Peter Baptizing the
Centurion; Liborio Fattori and Pietro Cardoni on St
Philip Baptizing the Eunuch; Enrico Enuo and Silverio de
Lelii on St Sylvester Baptizing Constantine; Alessandro
Cocchi and Giovanni Fiani on Christ Baptizing St Peter;
Alessandro Cocchi and Bernardino Regoli on Moses
Striking Water from the rocks; and Nicolo Onofre and
Bernardino Regoli on Noah Praying before the Rainbow.
The mosaics in the vault were done from 1739 to 1746
by Enrico Enuo, Domenico Gossoni, Giovanni Fiani,
Liborio Fattori, Pietro Cardoni, Prospero Clori, Nicolo
Onofri, and Alessandro Cocchi.
In the tambour of the dome there are four statues of angles
that are often overlooked.