Iran's Qara Kelisa will honor the memory of Saint Thaddeus and his faithful followers during a ceremony in the northern province of West Azarbaijan.

Scores of Armenians, Assyrians and Catholics from Iran and other countries will attend the annual event as part of their pilgrimage on the Day of St. Thaddeus.

The ceremony is known as one of the largest religious ceremonies held by Armenians, CHTN reported.

Qara Kelisa, also known as the St. Thaddeus Church, is one of the oldest and most notable surviving Christian monuments of Iran that carries great significance for the country's Armenian Orthodox community.

Armenians hold that Qara Kelisa is the world's first church and was constructed in 68 CE by one of the apostles of Jesus, Saint Thaddeus, who traveled to Armenia, then part of the Persian Empire, to preach the teachings of Christ.

Qara Kelisa, which literally means Black Church, has been registered as the ninth Iranian historical-cultural heritage site on the United Nations Educational Scientific and Cultural Organization's (UNESCO) World Heritage List.

The church is composed of two parts: a black structure, the original building of the church from which it takes its name and a white structure, the main church, which was added to the original building's western wing in 1810 CE.

An ancient chapel two kilometers northwest of the church is said to have been the place where the first Christian woman, Sandokh, was martyred. The chapel is believed to be as old as Qara Kelisa.

The structure was inscribed along with two other monastic ensembles of the Armenian Christian faith namely St. Stepanos and the Chapel of Dzordzor.