The Basilica of Saints John and Paul on the Caelian Hill was built in 398 AD over the home of two Roman soldiers, John and Paul, martyred under the emperor Julian in 362. The church was thus called the Titulus Pammachii and is recorded as such in the acts of the synod held by Pope Symmachus in 499.
The church was damaged during the sack by Alaric I (410) and because of an earthquake (442), restored by Pope Paschal I (824), sacked again by the Normans (1084), and again restored, with the addition of a monastery and a bell tower.
The church has three naves, with pillars joined to the original columns. The altar is built over a bath, which holds the remains of the two martyrs. The apse is frescoed with Christ in Glory (1588) by Cristoforo Roncalli. Below this fresco are three paintings: a Martyrdom of St John, a Martyrdom of St Paul, and the Conversion of Terenziano (1726) by Giovanni Domenico Piastrini, Giacomo Triga, and Pietro Andrea Barbieri.
During excavations performed in the 19th century, a series of Ancient Roman rooms were discovered under the nave of the church. Some of these rooms date back to the first and fourth centuries AD. In one room an elegant third-century AD fresco depicting Proserpine and other divinities among cherubs in a boat can be found, as can traces of another marine fresco and mosaics in the window arches.
References:The Church of St Donatus name refers to Donatus of Zadar, who began construction on this church in the 9th century and ended it on the northeastern part of the Roman forum. It is the largest Pre-Romanesque building in Croatia.
The beginning of the building of the church was placed to the second half of the 8th century, and it is supposed to have been completed in the 9th century. The Zadar bishop and diplomat Donat (8th and 9th centuries) is credited with the building of the church. He led the representations of the Dalmatian cities to Constantinople and Charles the Great, which is why this church bears slight resemblance to Charlemagne's court chapels, especially the one in Aachen, and also to the Basilica of San Vitale in Ravenna. It belongs to the Pre-Romanesque architectural period.
The circular church, formerly domed, is 27 m high and is characterised by simplicity and technical primitivism.