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.
qibla wall ⟂ direction of the Kaaba; mihrab on the axis
Muslim prayer is performed in rows facing the Kaaba in Mecca, so a mosque is less a building round a centre than a wall with people lined up before it. The qibla wall is usually the longest and most elaborate wall in the building; the prayer hall is broad rather than deep, so that as many worshippers as possible can stand in the front rows. The mihrab, a niche in the middle of the qibla wall, does not contain anything: it marks the direction and, acoustically and visually, the place of the prayer leader.
Finding the qibla was a real problem of spherical astronomy, and medieval scientists wrote treatises on it. In practice many early mosques follow local conventions (in Córdoba the qibla faces roughly south, the direction of the qibla in Damascus), a reminder that orientation was a matter of tradition as well as calculation.
To turn a domed square into a long church, open two of its great arches into semidomes of the same radius, and open the semidomes in turn into smaller exedrae, so that the space expands by stages from the central dome.
Hagia Sophia: central square 31 m; two semidomes of radius ≈ 15.5 m; four exedrae; interior ≈ 31 × 70 m
Where the ground is flat and the water lies deep, raise it from wells by wheels into tanks and channels, and lay the garden out in regular, symmetrical plots round them, with walks, beds of flowers and trees in order.
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.
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.
hall = n aisles × m bays of one module
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.
Place an iwan (a vaulted hall walled on three sides and open on the fourth) at the middle of each side of the courtyard, the one on the qibla side leading to a domed chamber before the mihrab.
Cite this page Chris Paton, “Everything turns to the qibla”, The Textbook of Architecture, https://textbookofarchitecture.com/rule/qibla-orientation. Text, drawings and models licensed under CC BY-NC 4.0.