Khor Virap ( lit. 'deep dungeon') is an Armenian monastery located in the Ararat Plain in Armenia, near the closed border with Turkey, about 8 kilometres (5.0 mi) south of Artashat, Ararat Province, within the territory of ancient Artaxata. The monastery was host to a theological seminary and was the residence of Armenian Catholicos. Khor Virap's notability as a monastery and pilgrimage site is attributed to the fact that Gregory the Illuminator was initially imprisoned here for about 14 years by King Tiridates III of Armenia. Saint Gregory subsequently became the king's religious mentor, and they led the proselytizing activity in the country. In the year 301, Armenia was the first country in the world to be declared a Christian nation. A chapel was initially built in 642 at the site of Khor Virap by Nerses III the Builder as a mark of veneration to Saint Gregory. Over the centuries, it was repeatedly rebuilt. In 1662, the larger chapel known as the "St. Astvatsatsin" (Holy Mother of God) was built around the ruins of the old chapel, the monastery, the refectory and the cells of the monks. Now, regular church services are held in this church. It is one of the most visited pilgrimage sites in Armenia.