The Sasanian caravanserai of Dayr-i gachīn, south of Ray, Iran

Numerous Arab geographers and Persian literary texts refer with a variety of detail to an important desert caravanserai known as Dayr-i gachīn (Ar. Dayr al-jiss), situated to the south of Ray. The word dayr , meaning in Arabic ‘monastery’, or perhaps ‘hospice’, seems a natural term for a caravanserai. That the term could also mean a domed building and a fire temple is suggested by both the Burhān-i qāti ' and the Farhang-i Ānandrāj . The Burhān-i qāti ', under ‘Khwarnaq’, states: Khwarnaq is the arabized word for Khuwarna, and this was a most excellent building which was built for Bahrām-i Gūr by Nu'mān b. Mundhir … and the other palace, which had three domes, one inside the other, and was built as a temple and a place of worship, they called Si-dayr since in Pahlavi they call a dome ‘ dayr ’.