A painting exhibition is currently underway at the St. Thaddeus Monastery, in the northwestern Iran, marks the 12th anniversary of the religious center’s inclusion on UNESCO World Heritage list.

The exhibition, which displays 77 paintings by children and teenagers, was inaugurated by the Prelate of Northern Iran Archbishop Kirkor Chiftdjian, according to a report in Tehran Times  on Wednesday.

The monastery, also known as Gharakilise, is one of the oldest surviving Christian monuments in Iran and it borders Armenia.

The ancient church features elaborate bas-reliefs of flowers, animals, and human figures on its façade and exterior walls. It bears verses of the Old and New Testament in Armenian calligraphy as well.

St. Thaddeus Monastery hosts an annual pilgrimage every summer. Last July, more than 3,000 worshippers come together from Armenia, Syria, Lebanon, the Netherlands, France, Austria, Germany, Canada and other countries.

Baptism of children and youngsters along with performances of traditional songs and dances are among highlights of the pilgrimage. The event is an important centerpiece for Iranian-Armenians who mostly flock there from nearby cities of Tabriz and Urmia, as well as farther cities of Tehran, Isfahan, and Ghazvin.

The annual pilgrimage is held to commemorate the martyrdom of St. Thaddeus, one of the twelve disciples of Jesus killed while he was preaching the Gospel. Legend has it that a church dedicated to him was first built in 68 AD where the St. Thaddeus Church still stands.

Together with St. Stepanos Monastery and the Chapel of Dzordzor, the St. Thaddeus Monastery was placed on the UNESCO World Heritage list in 2008 under the name “Armenian Monastic Ensembles of Iran.” UNESCO says that the churches bear examples of the outstanding universal value of the Armenian architectural and decorative traditions.