It was an old Roman pagan temple known as Baalbek Jupiter temple or “Heliopolitan” temple meaning the small temple of the sun, compared to the main Jupiter temple “Heliopolis” meaning the big temple of the sun in Baalbek. In ancient times 7 temples were located in the region, in reference to the 7 days of the week to worship the God of sun. Jupiter was the highest of gods. With the spread of Christianity especially during the 2nd, 3rd and 4th centuries AD, the temple was transformed into a church holding the name of Saint Barbara. Some historians say that the Saint became a Christian early on in her life in Ras Baalbek where she lived, but her father brought her to Baalbek where he murdered her to please the governor.

The church contains a big arcade and a 40-meter water channel carved in rocks, leading to a water spring in Ras Baalek in the main square of the town. The church contained a large pool designed for sacrifices used in the pagan era. The water channel is currently used to water the agricultural lands located at the right side of Ras Baalbek.

The stones in the temple are uncut and they are still natural taking the form of the church which contains the bases of the Roman Baalbek Jupiter temple. However, a French architect once mentioned the northern wall that was built in an anti-seismic way, using big and small stones in a specific alignment to avoid collapse.

It is estimated that the church was built between 325 and 350 AD.