(Collecta: Ss. Giovanni e Paolo)
(Image source)
From the Churches of Rome wiki:
The first church was consecrated in the time of Pope St Simplicius I (468-483), or possibly in 460, to hold the relics of St Stephen, protomartyr of the Church. His tomb had been discovered Kafr Gamala in the Holy Land in 415. It was later rededicated to St Stephen of Hungary. This was the first circular church in Rome, and it was modelled on the Church of the Holy Sepulchre in Jerusalem. The circumference and diameter of Santo Stefano is almost exactly the same as those of the Holy Sepulchre. Strangely, the church does not appear among the tituli in the synod list of 499. It is thought that it may have been financed by the wealthy Valerian family, whose estates covered large parts of the Coelian Hill. St Melanie, a member of this family, was a frequent pilgrim to Jerusalem and died there, so the family had connections to the Holy Land. The site housed the Castra Peregrinorum, a large army barracks with an ancient pagan sanctuary to Mithras, a deity that was very popular among soldiers. A gold-covered head from a statue of Mithras was found during excavations beneath the church.
It was decorated by Pope John I (523-526) and Pope Felix IV (526-530).
The colonnades were altered by Pope Innocent II (1130-1143), when a series of transverse arches were introduced to support the roof.
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The painting in the apse shows Christ between two martyrs. The mosaic and marble decoration is from the period 523 to 530. One mosaic shows the martyrs Primus and Felician flanking a jewelled cross. They were martyred in 305, and their relics were brought here by Pope Theodore I.
On the left is a tablet recording the burial here of the Irish king Donough O'Brien of Cashel and Thomond, son of Brian Boru, who died in Rome in 1064.
An ancient chair in which Pope Gregory the Great sat to deliver one of his homilies, in c. 580, is preserved here.
To the left by the entrance is the Chapel of Sts Primus and Felician. The chapel was commissioned by Pope Theodore I (642-649). The saints are depicted in a 7th century mosaic, and there are also frescoes depicting their martyrdom and burial. This is one of the rare examples of 7th century mosaic in Rome...
