"the gates of the sanctuary-screen"
The Iconostasis in the Cathedral of the Annunciation, Moscow
Public DomainThe Iconostasis in the Cathedral of the Annunciation, Moscow

 In Russian Orthodox churches the altar (or sanctuary) is usually separated from the rest of the church by a sanctuary screen, also called an iconostasis. These are covered in icons and highly decorated. In theological terms, the iconostasis acts as a link between the heavenly inner space of the altar and the holy space of the nave.