The Sahn's Roots in Arabian Domestic Architecture

The courtyard mosque plan did not appear from nothing; it adapts a domestic architectural form already established in pre-Islamic Arabia, where houses were commonly organized around an open central court ringed by rooms. The Prophet's Mosque at Medina, built adjoining Muhammad's own house, followed exactly this domestic logic: an open yard bordered by a covered area of palm trunks and thatch on the side facing Mecca, with rooms for his household along another side. As the early Islamic conquests produced permanent congregational mosques across a rapidly expanding territory, this simple courtyard-and-shaded-hall arrangement became the template for the hypostyle mosque, seen at scale in foundations such as the Great Mosque of Kairouan in Tunisia and the Great Mosque of Damascus, both of which preserve a large sahn bordered by riwaqs on three or four sides with a deep hypostyle prayer hall on the qibla side.

The form proved durable for over a millennium in regions with compatible climates, though it is not universal: the four-iwan plan that developed later in Iran and Central Asia keeps the open courtyard but frames it with four monumental vaulted iwans rather than continuous colonnades, and mosques built in colder or wetter climates, particularly in parts of Anatolia and China, often reduce or fully enclose the courtyard, replacing its ventilating function with domed or covered halls instead.