I know a bit about the influence of the Hagia Sophia on Ottoman mosque architecture! It really did influence many of the mosques in Istanbul, particularly Suleymaniye and Sultanahmet.

The scholar Rowland Mainstone points out the advantages of the Hagia Sophia’s “unique interior space” for Islamic worship: “With the fall of Constantinople and the conversion of Justinian’s church to serve as the first mosque, they at last had direct experience of its unique interior space, and the merits of its great unobstructed nave for their own simpler type of prayer."

There are two Ottoman mosques in Istanbul that are particularly reminiscent of the Hagia Sophia. The Suleymaniye and Sultan Ahmed mosques are probably the two buildings most emblematic of the city, along with the Hagia Sophia. Architecture professor Dr. Saqer Sqour calls the Ottoman conquest of Constantinople a turning point for Islamic architecture, stating that the majority of large Ottoman mosques follow the architectural style of the Hagia Sophia.

There is a striking visual similarity between the three buildings. The Sultan Ahmed mosque, in particular, almost certainly mirrors the Hagia Sophia intentionally, as the two buildings are located in the same complex and face each other across what is now a public courtyard and park. While domed mosques date back to far before the Ottoman period, it is clear that Ottoman mosques, at least, were influenced by the architecture of the Hagia Sophia. For example, the Dome of the Rock, built in the 7th century, features a dome, but its dome is based on an octagon, while the Hagia Sophia, Suleymaniye, and Sultan Ahmed mosques feature a dome atop a square base. This seems like a small difference, but it is key to identifying the Byzantine influences. The Hagia Sophia is one of the largest and earliest examples of the use of pendentives—triangular sections of a sphere used to connect the square of a building to the circle of a dome. This allows for the building of larger domes.

Further, the Hagia Sophia combines the Christian basilica structure and a central dome construction into a very innovative building. Christian basilicas are rectangular with three (or more) aisles divided by rows of columns. It was a very common floor plan for early Christian churches. The Suleymaniye Mosque, built in the 1550s, follows a similar rectangular floor plan, and its architect, Sinan, is known to have been influenced by the Hagia Sophia. In fact, Sinan was raised in a Christian household, but converted to Islam and is probably the most well-known Ottoman architect. In a way, his life follows the same arc as the architecture of the Hagia Sophia.