Early Christian communities appeared in the Balkans as early as the middle of the 1st century. A couple of centuries later, there were so many followers that dozens of them were martyred for their faith during Roman persecutions.

It is hardly a surprise that soon after Christianity was officially recognised, in 313, local Christian communities flourished. Bishoprics were set up, the flock increased and ecclesiastical councils discussing complex religious ideas were organised, attracting participants from all over the Roman world. By the end of the century, when Christianity became the empire's dominant and official religion, the Balkan communities started building sumptuous churches, both to accommodate the growing number of believers, and to show to the world the power of the new religion.

Most of the early churches which were built in what is now Bulgaria were basilicas – long three-nave buildings with an apse at the eastern end.

These early centres of Christianity declined in the late 6th and 7th centuries, when waves of pagan Barbarians settled in the Balkans. The religion revived once more in the 9th century, when Bulgarian Prince Boris recognised its potential as a political tool and a unifier of the different nations in his state.

Some of these churches have survived the centuries. Here is an overview of five of the most outstanding.

Belovska Basilica

You need to make an effort to see this one: you either hike for about 1.5 hours up a steep path that starts from Golyamo Belovo Village, or drive for 20 minutes with a 4WD on an unpaved road that starts from Belovo itself. Whichever way you reach this 6th century church, you will be rewarded with the picturesque sight of red arches rising over the thick forest that covers this part of the Rhodope mountains.

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In its heyday, the basilica was part of a large monastery and served the inhabitants of a nearby fort, Lefka, that protected a busy crossroads between the Rhodope, the Sofia plain and the Thracian plain.

According to legends, the church was destroyed by the Ottomans in the 17th century, during a campaign of forcible Islamisation of local people. Many historians, however, warn that such stories should be taken with a large pinch of salt.

The church may have fallen into ruin but the memory of the sanctity of the site persisted. People continued to go there to pray – a tradition whose latest manifestation is a relatively new chapel erected in the rest area beside the Belovska Basilica.

The early Christian ruins were rediscovered in the 19th century, and the site was excavated for the first time, with US funding, in 1924 by the Hungarian archaeologist André Grabar. The Belovska Basilica underwent conservation work in 1994.

The Old Metropolitan, Nesebar

Established by the ancient Greeks on the Black Sea coast, Nesebar became a centre of Christianity as early as the 4th century, and today boasts more than 40 churches crammed into the tightly-packed Old Town.

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The Old Metropolitan is the most impressive of Nesebar's early churches. Today this is a shell of a basilica – empty and roofless, frequented only by tourists. When it was built, in the late 5th or early 6th century, it was a marvel; a 22.5-metre-long three-nave church decorated with mosaics. It stood in the town square, probably over the ruins of a pagan temple, and was thoroughly reconstructed in the 10th century.

The greatest treasure of this church was the holy relics of St Theodore. In 1257, they were stolen by Venetians during the sack of Nesebar and taken to La Serenissima. By the end of the 18th century the church was abandoned, and religious life concentrated in a number of later, medieval churches which still fill the narrow streets of the town.

Elenska Basilica

Situated on a lush meadow near the mining town of Pirdop, the Elenska Basilica is an imposing redbrick ruin with three apses and vaults rising to 9 metres. Some say it was built as early as the 4th century, but construction in the late 5th or the early 6th centuries is more probable. The basilica was the heart of the monastic community of St Elijah, and was protected by a strong wall against the attacks of the Barbarians, which by that time had become a regular occurrence.

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The monastery survived the Ottoman conquest of the late 14th century, and over the next three centuries the monks of St Elijah became guardians of Bulgarian culture, because of their industrious work in the local scriptorium. In 1700, however, the monastery was attacked and destroyed by an Ottoman commander.

It is unclear why the locals renamed the church of St Elijah Elenska Basilica. According to one legend, St Helena, the mother of Emperor Constantine, stopped here on her return from the Holy Land carrying the True Cross. Her visit made a deep impression on the local people and when they built the basilica, they named it after her.

Despite its current state of dilapidation, the Elenska Basilica still has a place in local religious life. An old cross-shaped tombstone, probably from the 19th century, stands where the altar used to be, and there is someone who always places flowers and lights candles there.

Bishop's Basilica of Philippopolis, Plovdiv

The Late Antiquity churches of Plovdiv stand out because of their gorgeous mosaics. During the 4th century Philippopolis was an active centre of Christianity, and particularly of Arianism, the rejection of the divine nature of Christ. While bishops condemned Arianism as a heresy at a special council in Serdica (now Sofia), in 343, Philippopolis hosted a counter council. Its organisers were other bishops, the ones who adhered to Arianism.

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There are several buildings from that period in Plovdiv today, and by far the most spectacular is the Bishop's Basilica. Erected in the 4th century in what was then the centre of the town it is 90 metres long and 36 metres wide, the grandest Late Antiquity basilica in the modern Bulgarian lands. What makes it so special is not the size, however. It is the two layers of floor mosaics, a total of 2,000 square metres. The lower layer represents an intricate web of geometrical ornaments and symbols in various colours, creating a near 3D effect. The upper layer depicts over 100 birds, symbolising the souls of the faithful that longed for God.

The Bishop's Basilica of Philippopolis is also a good example of spiritual continuity. It was erected over the remnants of an earlier building, probably a pagan temple. After the 6th century, when the basilica had been abandoned, some houses were built over it. In the 10th-13th centuries the site was a large Christian necropolis with a richly decorated church. Then, in the mid-19th century, next to what was already a long-forgotten cemetery, the St Ludwig Roman Catholic Cathedral was constructed.

In the 2010s, the Bishop's Basilica of Philippopolis was researched and revived as a visitor centre that uses VR technologies and mosaic preservation to tell the story of the site in a way that appeals to modern audiences. The project was funded by the America for Bulgaria Foundation and Plovdiv Municipality. 

Red Church, Perushtitsa

Originally, the church near Perushtitsa bore the name of the Virgin, but in time memories faded and the local people started to call it simply The Red Church. It is easy to see why. What has remained of this once glorious structure are massive redbrick walls and arches reaching 14 metres in height.

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The church was built at the end of the 5th or the beginning of the 6th century and was part of a large-scale construction effort to promote Christianity; the initiative of the bishops in nearby Philippopolis.

It is 32 metres long and 26 metres wide, and has three apses meeting under a huge cupola, forming the shape of a trefoil. Exquisite mosaics covered the floors, and marble and murals decorated the walls. The church was painted at least twice, in the 6th and the 11th centuries, and despite the decayed state of the frescoes, some historians have compared them to those in Istanbul's Hagia Sophia. Believers entered the church via a grand staircase and a massive portico, while non-Christians were baptised in a pink marble baptistry attached to the main building.