Persian architecture

Picture a hall with three walls and a vault. The fourth side is completely open. That is an iwan – and it is older than Islam.

The Parthians build the first ones, in Mesopotamia around the beginning of our era. The Sasanians make them enormous. At Ctesiphon the Taq Kasra still stands from around 540, a brick arch that was the largest vault in the world in its day.

Then comes Islam, and the iwan moves into the mosque. In the 12th century the Friday Mosque of Isfahan gets four iwans around its courtyard – a plan Iran never lets go of.

The peak comes with the Safavids. Shah Abbas I makes Isfahan his capital and lays out a square larger than almost any other: Naqsh-e Jahan. Around it rise palaces, a bazaar and two mosques. The Shah Mosque is begun in 1611. Everything is clad in tile – now in a new, faster technique, haft rangi, where seven colours are painted on the same tile and fired at once. The dome is double: one shell for the room inside, a taller one for the city outside. The architect's name, Ali Akbar Isfahani, is in the foundation inscription above the portal.

Why so much blue? It is the colour of the sky in a land of desert dust and clay. Inside the courtyard it turns cool, green and blue – a paradise behind the walls.

Seljuk architecture. The Seljuks build the iwans in Isfahan and pattern with brick. Blue tile covering whole façades belongs to the later Persian dynasties, above all the Safavids.

Moorish architecture. It too has courtyards with water, but the arches are horseshoe-shaped and the decoration is stucco rather than blue tile.