A templon (from Greek τέμπλον meaning "temple", plural templa) is a feature of Byzantine churches consisting of a barrier separating the nave from the sanctuary near the altar.
The solid templon first appeared in Christian churches around the 5th century and is still found in many Eastern Christian churches. Initially it was a low barrier probably not much different from the altar rails of many Western churches. It eventually evolved into the modern iconostasis, still found in Orthodox churches today.
It is usually composed of carved wood or marble colonnettes supporting an architrave (a beam resting on top of columns). Three doors, a large central one and two smaller flanking ones, lead into the sanctuary. The templon did not originally obscure the view of the altar, but as time passed, icons were hung from the beams, curtains were placed in between the colonnettes, and the templon became more opaque. In modern Orthodox churches, it is common for the openings of the templa to be constructed specifically to contain icons.