Although in the eyes of the Byzantines this religion was pagan, it laid the solid foundation on which the ancient Bulgarians built their society.
After Khan Asparukh crossed the Danube and built his new capital, Pliska, he took a number of actions aimed at stabilising the new state union. Large-scale constructions began. Along the borders, earth mounds and ditches to stop the enemies, and in the capital and the larger fortified auls, temples were built. These sanctuaries and temples are associated with the cult of the supreme god of the ancient Bulgarians. The rituals were performed in them by priests, specially prepared and trained, called the “kolobaris”. Initiated to the secrets of nature and possessing higher knowledge and wisdom, they were bearers of that age-old wisdom and knowledge that have accompanied the mighty Bulgarian people since the dawn of time. Although seen as pagan by the Byzantines, the temples of the Proto-Bulgarians are indisputable evidence of the ancient roots of their civilisation.
The first archaeological finds from temples were discovered during the excavations in Pliska. Remains were found in the vicinity of the palace, they were the foundations of a large rectangular building, with massive foundations of worked stone blocks. Its orientation is in the east-west direction, and traces have been found that after the adoption of Christianity, it was converted into a church.
Madara is mentioned as one of the main cult complexes, where the Bulgarian rulers and priests performed rituals and sacrifices and revered the supreme god. The main example of the temples there has a plan similar to the one found in Pliska.
Archaeological excavations over the years have uncovered many more sites of temples. Most of them had a rectangular or square shape, but some, such as those in Durankulak and Balchik, had a round one. Undoubtedly, the Proto-Bulgarians used various approaches and techniques to build their spiritual centres, in order to worship the supreme god and perform their rituals. Despite the form, however, all Proto-Bulgarian sanctuaries followed a strictly defined plan, which shows that in its essence the religion of the ancient Bulgarians had a serious basis. Some of the temples were located on the sites of the ruler's residences. In this way, they were closely connected with the religious functions that the supreme Khan performed together with the administrative and secular power he carried himself.
Proto-Bulgarian temples, despite their shape, consisted of two parts: internal and external. The inner part had thicker and more massive foundations than the outer one. The latter was tightly closed, but was sometimes also surrounded by colonnades. The inner part of the temple was covered with a dome - in the temples with a square plan, or a cylindrical vault in the temples with a rectangular shape. There was an altar in the temples. It consisted of a short base, a short column and an altar stone. The sacred fire burned on it.
There were water pools in the Proto-Bulgarian temples. Its use was necessary for the performance of ceremonies and ritual purification. Each Proto-Bulgarian temple was supplied with water from a natural water source or a specially dug well. The ritual objects used in the ceremonies were washed and the priests also bathed with water.
Water as an element was revered as much as fire. It symbolised peak physical health and infinity. The cult of water and purity is evidenced by preserved sources, which describe the religious acts performed by Khan Krum in front of Constantinople. The Bulgarian ruler ritually stepped into the sea, then washed himself with water and sprayed his soldiers with it.
The religion of the Proto-Bulgarians remains a blur, although it had its ceremonies and sacred places. It was practiced mainly by the ruling elite : the Khan, his successors, the boyars and the priestly class, which had a complex hierarchical system and titles.
Thus, in those troubled times, following the same moral principles, customs and spiritual path, the Proto-Bulgarians managed to establish themselves as a cohesive community and together to cope with the difficulties and challenges of the time. The unified religion helped the country to have a strong centralised power, and to strictly observe the principle unique leader and unquestioning obedience to the will of the supreme ruler. Although the Proto-Bulgarians were tolerant of other religions, as there were among them many who had converted to Christianity, the faith in the supreme god was revered as it should be, and the sacred temples were erected in his honour. And although in later times the opposition between Christians and the followers of the old religion became particularly bitter and led to certain internal conflicts in the state, in essence the role of the temples did not change much. The temples erected before, in which the Supreme God was worshiped, were for the most part rebuilt into churches and monasteries, where the wisest and most skillful of the Bulgarians continued to develop their skills, arts and spiritual life in a way that aimed to preserve and transmit the ancient, spiritual and cultural heritage, to preserve customs and traditions.