The mosaic theme at St. Praxedes relates to the second coming of Christ as revealed in Revelation, the last book of the Bible.
The decoration of the apse illustrates Christ, at the end of time, blue cross within His halo, holding a scroll in his left hand, with right arm raised to show the palm scars of crucifixion, being crowned by the hand of God.
On his left is St. Peter with his arm around St. Pudentiana whom he presents to God. To her left an undentifiable deacon wearing a typical liturgical robe. To the right of Christ St. Paul presents St. Praxedes. The crowns held by the sisters indicates their martydom. Pope Paschal I, with monogram above the hand of God, presents a model of the church he built. The square halo is the sign of a person still living.
The group of seven is framed by palm trees representing Paradise and Victory with the named river Jordan beneath their feet.
Below the figures, Christ is represented by the Easter lamb atop a mound from which flow the four rivers of Paradise. Twelve lambs representing the twelve Apostles stand between Bethlehem on the left and Jerusalem on the right.
The Arch of the Apse continues to illustrate passages from the book of Revelation. Within the central medallion the Lamb of Christ lies on a throne above a book with seven seals. To the sides, seven lamps are identified as the seven churches of Asia, then four angels and four living beings. The latter, each with six wings are usually considered as symbolic of the four evangelists; the man for Matthew, the lion for Mark, the bull for Luke, the eagle for John. Below are twenty four elderly men dressed in white, offering gold crowns of wisdom.
Revelation's ideal of Paradise is represented in the Arch of Triumph. Within the walled city of Jerusalem is Christ with two angels, the Virgin Mary, John the Baptist and St. Praxedes, flanked by apostles and saints with Moses and prophet Elias. The gates are guarded by angels and on either side an angel with unfolded wings leads a multitude of 144,000 saved souls to the city. To the left are martyrs and bishops. To the right, a group led by apostles Peter and Paul. The crowds of believers in the lower register are also described in Revelation.