Architecturally unique, the Shahjahan mosque is distinct in its layout as well as in its materials. It is the first mosque in this region to be constructed according to the principles of Mughal courtyard architecture. Atypical of mosques, this building is elongated along the east-west rather than the usual north-south axis. Red brick is utilized rather than the pink sandstone and marble more commonly associated with Mughal buildings. Quite likely, the decision to use brick was made out of practical concerns of cost and availability, since Thatta does not have much stone. The surfaces are decorated with glazed tiles.
The mosque was commissioned by the Mughal emperor Shah Jahan as a gesture of gratitude to the people of Thatta for sheltering him during his youth after his father Emperor Jahangir banished him from Delhi. Several Persian inscriptions on site date the foundation of the mosque to 1644 and its completion to 1647. The floor was paved with stone in 1657. Repair work done during the seventies by the Endowment (Awqaf) Department added a garden to the eastern side.
The freestanding entrance built for the new garden is defined by a triple arched structure that imitates the Mughal style of arches contained within rectangular frames, with the central portion being projected higher than the others. It is built on axis with the main entrance to the mosque. The new garden is an imitation of the four-quadrant chahar bagh style, through which one walks to reach the mosque.
Other equally interesting modifications and experiments with Mughal style are also in evidence; for example, there is no minaret. Instead of the typical three bulbous domes, there is only one main dome in the prayer hall. The dome does not command a strong visual position, as it is completely concealed behind a tall semi-domed entrance (pistaq). The use of high pistaqs during the Takhan period of Thatta has been recorded and is also typical of the Timurid architecture. The concept of a domed iwan has been developed here and has been used to define the secondary entrances.
The Shah Jahan mosque represents the height of tile decoration in the Sind. The influence of mosaic on tile work is seen in the ceiling decoration of semi-domed and domed chambers, as well as in the fillings of interlaced arches and in the panels at squinch level. The technique of soft glazed tile paneling had been in use since the Tarkhan period. Various shapes of tiles - square, rectangular and hexagonal - were manufactured and joined to complete a design in a given panel. The tilework is not related to the imperial Mughal style, but to the Timurid school. Various shades of blue on white, and some yellow or purple background produce a very soothing effect in the hot climate of Thatta.
p.s. I've used PS to remove a distracting cellphone tower from the right of the image.