The sanctuary or chamber is the place where God and Mankind meet and can converse. The natural symbol for this is the Universe which expresses the infinite creativity of God while enclosing mankind in a protective space. Amongst the innumerable ways of concretising the Universe the architects of Iran developed the concept of a dome.
The Dome is thus a shape of great symbolic importance which must be replicated through the properties of matter. The earliest domes were formed of skins stretched over wicker frames, but by the time of Chosroes III attempts were already being made to build palaces whose domes mirrored the architecture of the heavens. They thus took on an astrological or mystical significance and came to symbolise mankind's attempts to create a heaven on earth.
Remnants of these early domes can be seen in the ribbed Seljuk constructions of the 11th century where the brick vaulting is reminiscent of the early constructions of wooden sticks and skins. It is also visible in the Beit Al-Sheita in the Friday Mosque, where the style of the vaulting is said to be inspired by the tents of the mongols which used the wicker fame and skin construction mentioned earlier: both of these are shown above.
The dome thus becomes a symbol of the cosmic house of God which in turn has a dual meaning of the House that God inhabits - Heaven, and the house that encompasses Man - The Universe. The dome acts therefore as a transition between the infinite unity of its central point, through the duality of its symbolism into the concretisation of the four-sided chamber which supports it and which symbolises the fourfold nature of mankind.