It is an ancient Armenian monastery located in the mountainous area of Iran, about 20 kilometers from the town of Maku.
The monastery is visible from a distance because of the massiveness of the church, strongly characterized by the polygonal drums and conical roofs of its two domes. There are several chapels nearby: three on the hills east of the stream, one approximately 3km south of the monastery on the road to Bastam, and another that serves as the church for the village of Ghara-Kilise.
One of the 12 Apostles, St. Thaddeus, also known as Saint Jude, (not to be confused with Judas Iscariot), was martyred while spreading the Gospel. He is revered as an apostle of the Armenian Apostolic Church. Legend has it that a church dedicated to him was first built on the present site in AD 68.
Not much appears to remain of the original church, which was extensively rebuilt in 1329 after an earthquake damaged the structure in 1319. Nevertheless, some of the parts surrounding the altar apse date from the 10th century.
Most of the present structure dates from the early 19th century when Qajar prince Abbas Mirza helped in renovations and repairs. The 19th century additions are from carved sandstone. The earliest parts are of black and white stone, hence its Turkic name Kara Kilise, the Black Church.
A fortified wall surrounds the church and its now-abandoned monastery buildings.
In July 2008, the St. Thaddeus monastery was added to UNESCO’s World Heritage List, along with two other Armenian monuments located in the same province: Saint Stepanos Monastery and the chapel of Dzordzor.