Serdica in the context of "Council of Sardica"

Sofia is the capital and largest city of Bulgaria. It is situated in the Sofia Valley at the foot of the Vitosha mountain, in the western part of the country. The city is built west of the Iskar river and has many mineral springs, such as the Sofia Central Mineral Baths. It has a humid continental climate.

Known as Serdica in antiquity, Sofia has been an area of human habitation since at least 7000 BC. The recorded history of the city begins with the attestation of the conquest of Serdica by the Roman Republic in 29 BC from the Celtic tribe Serdi. During the decline of the Roman Empire, the city was raided by Huns, Visigoths, Avars, and Slavs. In 809, Serdica was incorporated into the First Bulgarian Empire by Khan Krum and became known as Sredets. In 1018, the Byzantines ended Bulgarian rule until 1194, when it was reincorporated by the Second Bulgarian Empire. Sredets became a major administrative, economic, cultural and literary hub until its conquest by the Ottomans in 1382. From 1530 to 1836, Sofia was the regional capital of Rumelia Eyalet, the Ottoman Empire's largest and most important province. Bulgarian rule was restored in 1878. Sofia was selected as the capital of the Third Bulgarian State in the next year, ushering a period of intense demographic and economic growth.

Heraclea Lyncestis, also transliterated Herakleia Lynkestis (Ancient Greek: Ἡράκλεια Λυγκηστίς; Latin: Heraclea Lyncestis; Macedonian: Хераклеја Линкестис), was an ancient Greek city in Macedon, ruled later by the Romans. Its ruins are situated 2 km (1.2 mi) south of the present-day town of Bitola, North Macedonia. In the early Christian period, Heraclea was an important Episcopal seat and a waypoint on the Via Egnatia that once linked Byzantium with Rome through the Adriatic seaport of Dyrrachium. Some of its bishops are mentioned in synods in Serdica and other nearby towns. The city was gradually abandoned in the 6th century AD following an earthquake and Slavic invasions.

The Serdi were a Celtic tribe inhabiting Thrace. They were located around Serdica (Bulgarian: Сердика, romanized: Serdika; Latin: Ulpia Serdica; Greek: Σαρδική o Σαρδῶν πόλις, romanized: Sardike o Sardon polis), now Sofia in Bulgaria, which reflects their ethnonym. They would have established themselves in this area during the Celtic migrations at the end of the 4th century BC, though there is no evidence of their existence before the 1st century BC. Serdi are among traditional tribal names reported into the Roman era. They were gradually Thracianized over the centuries but retained their Celtic character in material culture up to a late date. According to other sources they may have been simply of Thracian origin; according to others they may have been of mixed Thraco-Celtic origin.

The Edict of Milan (Latin: Edictum Mediolanense; Greek: Διάταγμα τῶν Μεδιολάνων, Diatagma tōn Mediolanōn) was the February 313 agreement to treat Christians benevolently within the Roman Empire. Western Roman Emperor Constantine I and Emperor Licinius, who controlled the Balkans, met in Mediolanum (modern-day Milan) and, among other things, agreed to change policies towards Christians following the edict of toleration issued by Emperor Galerius two years earlier in Serdica. The Edict of Milan gave Christianity legal status and a reprieve from persecution but did not make it the state church of the Roman Empire, which occurred in AD 380 with the Edict of Thessalonica, when Nicene Christianity received normative status.

The document is found in Lactantius's De mortibus persecutorum and in Eusebius of Caesarea's History of the Church with marked divergences between the two. Whether or not there was a formal 'Edict of Milan'  is no longer really debated among scholars, who generally reject the story as it has come down in church history.

The gens Ulpia was a Roman family that rose to prominence during the first century AD. The gens is best known from the emperor Marcus Ulpius Trajanus, who reigned from AD 98 to 117. The Thirtieth Legion took its name, Ulpia, in his honor. The city of Serdica, modern day Sofia, was renamed as Ulpia Serdica.

Serdika or Serdica (Bulgarian: Сердика [ˈsɛrdikɐ]) is an administrative subdivision of Sofia, Bulgaria, named after the ancient city of Serdica.

The Serdika district includes four neighbourhoods: "Fondovi zhilishta"; "Banishora", "Orlandovtsi" and "Malashevtsi" as well as the central parts of "Draz mahala". It has an area of 17.53 km that counts for 1.3% of the total Capital Municipality area and 8.8% of the city proper. As of 2006 Serdica has a population of 52,918.

The Edict of Serdica, also called Edict of Toleration by Galerius, was issued in 311 in Serdica (now Sofia, Bulgaria) by Roman Emperor Galerius. It officially ended the Diocletianic Persecution of Christianity in the Eastern Roman Empire.

The Edict implicitly granted Christianity the status of religio licita, a worship that was recognized and accepted by the Roman Empire. It was the first edict legalizing Christianity and preceded the Edict of Milan by two years.

Dacia Aureliana was a province in the eastern half of the Roman Empire established by Roman Emperor Aurelian in the territory of former Moesia Superior after his evacuation of Dacia Traiana beyond the Danube in 271. Between 271/275 and 285, it occupied most of what is today northwestern Bulgaria and eastern Serbia. Its capital was in Serdica (modern Sofia).

This province was populated with a part of the former inhabitants of Dacia Traiana. It is written in Eutropius' work: Abridgment of Roman History (9:15):