Akdamar Island, also known as Aghtamar or Akhtamar, is the second largest of the four islands in Lake Van, in eastern Turkey. About 0.7 km² in size, it is situated about 3 km from the shoreline. At the western end of the island a hard, grey, limestone cliff rises 80 m above the lake's level. The island declines to the east to a level site where a spring provides ample water. It is home to the 10th century Armenian Holy Cross Cathedral, which was the seat of the Armenian Apostolic Catholicosate of Aghtamar from 1116 to 1895.