Ani, located in Eastern Turkey, was in the 10th Century the capital of an Armenian principality. In its prime, the city’s population was similar in size (100,000 — 200,000) to Constantinople, Baghdad, and Cairo. It became the seat of the Catholicoi, the head of the Armenian Apostolic Church in 992.
Ani was sacked by the Seljuk Turks in 1064, and by the Mongols in 1236. The city declined over subsequent centuries, ceasing to be a dynastic capitol around 1400, and losing the Armenian Catholicosate in 1441. Ani gradually dwindled to a small settlement within the walls of the former city, and was completely abandoned by the 18th century.
The site was excavated and documented by the Russian linguist and archaeologist Nicholas Marr 1892-93 and 1904-17.
Hat tip to Fred Lapides.