In the late ancient times, Salona's importance was great both politically and religiously.
 Salona was an early Roman settlement, which became overshadowed when Emperor Diocletian constructed the nearby Diocletian's Palace in about the year 300 AD.
Surviving local residents of Salona, after the Avars retreated from those regions, to a settlement "Spalatum", today's (Split), at the location of Diocletian's Palace (probably around the middle 7th century AD).
Christianity in Salona probably originated during the time of the apostles.

The Apostle Paul mentions that his pupil Apostle Titus traveled to Dalmatia  so the assumption that he worked in Dalmatia's capital city of Salona, at least for a short time, is probable.
That city, located on the Adriatic coast, with excellent sea connections with Italy and the Middle East, attracted Christian messengers of faith.

Salona had a well-organized Christian community with a bishop as leader ever since the middle of the 3rd century (bishop martyr Venantius lived at that time).
Since the fourth century, Salona honored in its large basilicas its glorious martyrs from the times of Diocletian's persecution: St Domnius (Latin: Domnius; Croatian: Duje; Italian: Domnio), craftsman Anastasius the Fuller, deacon Septimia, priest Asteria, and others.

In the fifth Century, Salona's bishops started exercising more metropolitan duties (archbishop Hezihius), and in the sixth century they carried the archbishop title as well (arhiepiscopus), and fulfilled the duties associated with the title. (
archbishops Stephen, Honorius and others).
That means that at that time they held primary positions in western Illyria.
Siscia's bishop from the region Pannonia joined the Dalmatian bishops on the synods held in Salona in the years 530 and 533 as a member with full rights.
At the time of Diocletian, Salona had a population of 60,000.

In 639 Salona was destroyed by the Avars.
 After the fall of Salona and the whole region under the Avarian rule (first quarter of 7th century), worship of Salona's martyrs was moved to Rome.
Namely, Pope John IV ordered transportation of parts of their relics, which he placed in a dedicated chapel close to the Lateran baptistry.
The images of those saints, which had been created in mosaic by the Pope's wish, can be found today in the apside of the chapel.
Search for relics for Rome was probably the incentive for Salona residents who inhabited the new city of Split, located only a few kilometers from the abandoned Salona.
At the very least, they wanted to bring to Split the bones of their most important protectors: St. Domnius and St. Anastasius.
They placed them in what was once Diocletian's mausoleum, which was subsequently converted into the Cathedral of Saint Domnius.
In the late ancient times, Salona's importance was great both politically and religiously.  Salona was an early Roman settlement, which became overshadowed when Emperor Diocletian constructed the nearby Diocletian's Palace in about the year 300 AD. Surviving local residents of Salona, after the Avars retreated from those regions, to a settlement "Spalatum", today's (Split), at the location of Diocletian's Palace (probably around the middle 7th century AD). Christianity in Salona probably originated during the time of the apostles.
The Apostle Paul mentions that his pupil Apostle Titus traveled to Dalmatia  so the assumption that he worked in Dalmatia's capital city of Salona, at least for a short time, is probable. That city, located on the Adriatic coast, with excellent sea connections with Italy and the Middle East, attracted Christian messengers of faith.
Salona had a well-organized Christian community with a bishop as leader ever since the middle of the 3rd century (bishop martyr Venantius lived at that time). Since the fourth century, Salona honored in its large basilicas its glorious martyrs from the times of Diocletian's persecution: St Domnius (Latin: Domnius; Croatian: Duje; Italian: Domnio), craftsman Anastasius the Fuller, deacon Septimia, priest Asteria, and others.
In the fifth Century, Salona's bishops started exercising more metropolitan duties (archbishop Hezihius), and in the sixth century they carried the archbishop title as well (arhiepiscopus), and fulfilled the duties associated with the title. (archbishops Stephen, Honorius and others). That means that at that time they held primary positions in western Illyria. Siscia's bishop from the region Pannonia joined the Dalmatian bishops on the synods held in Salona in the years 530 and 533 as a member with full rights. At the time of Diocletian, Salona had a population of 60,000.
In 639 Salona was destroyed by the Avars.  After the fall of Salona and the whole region under the Avarian rule (first quarter of 7th century), worship of Salona's martyrs was moved to Rome. Namely, Pope John IV ordered transportation of parts of their relics, which he placed in a dedicated chapel close to the Lateran baptistry. The images of those saints, which had been created in mosaic by the Pope's wish, can be found today in the apside of the chapel. Search for relics for Rome was probably the incentive for Salona residents who inhabited the new city of Split, located only a few kilometers from the abandoned Salona. At the very least, they wanted to bring to Split the bones of their most important protectors: St. Domnius and St. Anastasius. They placed them in what was once Diocletian's mausoleum, which was subsequently converted into the Cathedral of Saint Domnius.
Solin