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.
Rules · Domes · Structure · Façades
The double dome
Build two domes, one above the other: an inner shell proportioned to the room below and an outer shell raised on a tall drum and proportioned to the city outside.
outer crown ≫ inner crown; the gap may be a third of the total height
A single dome must serve two masters: seen from inside it should not be too high for the room, and seen from outside it should dominate the skyline. Iranian builders separated the two tasks. The inner dome is a low, well-proportioned vault over the prayer chamber; the outer dome, braced to the inner by radial walls and timber ties, rises on a tall drum and swells outward so that it can be seen from far away. At the Masjid-i Shah the outer shell rises about fourteen metres above the inner.
The idea travelled west to the Ottomans only in part, but east with the Timurids to India, where the Mughals made the outer shell bulbous and the gap enormous.
Related rules
Fill a half-dome, squinch or cornice with tiers of small concave cells, each tier corbelled forward from the one below and each cell set over the junction of two cells beneath.
height = tiers × module; each tier projects inward
Set the iwan arch in a tall rectangular screen that rises above the roofline, framed by bands of inscription and flanked by minarets.
Balance the tomb so that the dome with its finial rises as high above the pishtaq as the pishtaq rises above the plinth, and let every element be answered by its mirror image on both axes.
pishtaq ≈ dome + finial ≈ 33–35 m; total ≈ 73 m (approximate)
Cover the tomb chamber with a low inner dome and raise over it, on a tall drum, a bulbous outer shell whose swelling profile is visible from every direction.
Mark the corners of roofs, minarets and gateways with chhatris: small open domed kiosks on columns with a projecting eave.
Cite this page Chris Paton, “The double dome”, The Textbook of Architecture, https://textbookofarchitecture.com/rule/persian-double-dome. Text, drawings and models licensed under CC BY-NC 4.0.