A turbe (tomb) thought to have been built for Ertann Hassan by his son in 1347 at Sivas, Turkey (Medieval Sebastia, sometimes spelt Sebastea or Sebasteia). Sivas is the provincial capital of the Sivas Province in Turkey. In 1174, the city was captured by Seljuk ruler Kilij Arslan II and periodically served as capital of the Seljuk empire along with Konya. Under Seljuk rule, Sivas was an important center of trade and site of a citadel, along with mosques and madrasahs (religious educational institutions), four of which survive today and one of which houses the Sivas Museum. The city fell to the Ottoman Sultan Bayezid I (1389?1402) in 1398, was lost to Timur (Tamerlane) (1336?1405) in 1400, and was recaptured by the Ottomans in 1408. Under the Ottomans, Sivas served as the administrative center of the province of Rum until about the late nineteenth century.