The hypostyle mosque
Córdoba and Kairouan: a courtyard and a forest of columns carrying parallel arcades towards the qibla wall.
The rules it illustrates
Everything turns to the qibla. Orient the prayer hall so that its principal wall, the qibla wall, stands square to the direction of Mecca, and mark the middle of that wall with a niche, the mihrab.
Court and prayer hall. Build the congregational mosque as an enclosed courtyard (sahn) with a covered prayer hall (haram) on its qibla side and shaded porticoes (riwaq) on the others.
The hypostyle grows by addition. Make the prayer hall of identical bays of columns and arcades, so that it can be enlarged by adding aisles or bays without changing its character.
Arches on arches: height from short columns. Where the available columns are too short for the height you want, stand a pier on each column and carry the roof on a second, upper tier of arches, bracing the piers with a lower tier of horseshoe arches.
The horseshoe arch. Carry the curve of the arch beyond the semicircle, so that the opening at the springing is narrower than its greatest width.
Striped voussoirs. Alternate voussoirs of two colours (red brick and pale stone, or black and white stone) to make the structure of the arch legible as ornament.
The alfiz. Frame an important arch with a rectangular moulding or band rising from its springing, so that the curved opening is set within a square field.
The minaret takes the shape of its region. Build the tower for the call to prayer in the form of the regional tradition: square and stepped in the Maghreb and Spain, cylindrical and tapering in Iran and Central Asia, needle-like and polygonal in the Ottoman lands.
Where it appears in the book
In the styles Early Islamic (Umayyad and Abbasid), Moorish (Western Islamic).
In the chapters The Islamic World.