Blue Mosque (Sultan Ahmed Mosque): Istanbul's Ottoman Icon

The Blue Mosque, officially the Sultan Ahmed Mosque (Sultanahmet Camii), is an Ottoman imperial mosque in Istanbul, built between 1609 and 1616 for Sultan Ahmed I. Designed by the architect Sedefkâr Mehmed Ağa, it stands on the old Hippodrome facing Hagia Sophia, and is famous for its six minarets, cascading domes and interior of blue Iznik tiles. It was the last great mosque of the Ottoman classical age and remains both a working place of worship and one of the most visited buildings in the world.

Background: a young sultan and a costly vow

Ahmed I became sultan in 1603 at the age of thirteen. His reign began in difficult times. The Ottomans were fighting the Habsburgs in the Long Turkish War, which ended in 1606 without major gains, and in 1603 Shah Abbas of Iran had launched a war that cost the empire Tabriz and much of the Caucasus. At home, the Celali revolts disturbed Anatolia.

Ottoman sultans traditionally built great mosques in Istanbul to display their piety and power. Earlier sultans, such as Suleiman the Magnificent with the Süleymaniye Mosque, had paid for theirs from the spoils of victorious campaigns. Ahmed had no such victories. When he decided to build a vast mosque anyway, some religious scholars objected that it should not be funded from the state treasury. Ahmed went ahead, and the project became a statement of the dynasty’s prestige at a time of uncertainty.

The site and the architect

Choosing the site

The sultan chose a prominent site on the south-east side of the Hippodrome, the ancient chariot-racing ground of Constantinople, directly facing Hagia Sophia. Part of the area had once been occupied by the Great Palace of the Byzantine emperors.

To make room, several palaces of leading Ottoman statesmen, including one that had belonged to the grand vizier Sokollu Mehmed Pasha, were bought and demolished. The location placed the new mosque at the symbolic heart of the city, in dialogue with the great church that had been turned into a mosque in 1453.

Sedefkâr Mehmed Ağa

The architect, Sedefkâr Mehmed Ağa, was chief architect of the court. Born in the Balkans, probably in Albania, he was recruited through the devşirme, the levy of Christian boys for Ottoman service. He trained in mother-of-pearl inlay, the craft that gave him his nickname, before studying architecture, partly under the great Mimar Sinan.

His life and work are unusually well documented thanks to the Risale-i Mimariyye (“Treatise on Architecture”), written around 1614 by his admirer Cafer Efendi. It describes his career, his skills in geometry and craftsmanship, and his role in the mosque’s construction.

Design and decoration

Building the mosque

Work began in 1609 with a ceremony attended by the sultan, who is said to have helped dig the foundations. Thousands of workers, craftsmen and soldiers took part. The mosque itself was largely complete by 1616, and the wider complex took a little longer.

The design follows a plan developed by Sinan and inspired by Hagia Sophia: a large central dome supported by four semi-domes, creating a square prayer hall that feels open and unified. The central dome is about 23.5 metres in diameter and rises to about 43 metres. It rests on four massive fluted piers, about five metres across, sometimes called “elephant feet”.

Outside, smaller domes and semi-domes rise in steps towards the central dome, giving the building its famous pyramid-like silhouette. A large forecourt, as big as the prayer hall itself, is surrounded by a domed arcade and centred on an ablution fountain.

Tiles, light and decoration

The interior is lined with more than 20,000 handmade tiles from the workshops of Iznik, in dozens of designs of tulips, carnations, roses, cypress trees and fruit. The finest are on the lower walls and in the galleries. The huge order strained the Iznik workshops, and the quality of some later tiles is lower than those of the sixteenth century, a sign of the industry’s decline.

More than 200 windows, originally fitted with coloured glass, flood the hall with light. The upper walls and domes were painted, and much of this decoration was renewed in later centuries, sometimes in stronger blue tones that helped give the mosque its popular name. Calligraphic inscriptions of Qur’anic verses are attributed to Seyyid Kasım Gubari, a leading calligrapher of the time.

The marble mihrab, which shows the direction of Mecca, and the finely carved minbar, or pulpit, stand at the front of the hall. A raised royal loge allowed the sultan to pray apart from the congregation.

The six minarets

The mosque has six minarets, four at the corners of the prayer hall and two at the outer corners of the forecourt. This was unusual: most imperial mosques had four or fewer, so six minarets emphasised the sultan’s status.

A popular story says that the number caused offence because the Great Mosque of Mecca also had six minarets, and that Ahmed paid for a seventh at Mecca to restore its pre-eminence. Another tale claims the architect misheard “altın” (gold) as “altı” (six). Both are later traditions rather than documented events.

Visiting the mosque: what to look for

Most visitors enter through the forecourt, which gives a first sense of the building’s scale. From there, the eye is drawn upward along the stepped domes to the minarets, each with balconies from which the call to prayer was traditionally made. The four minarets at the corners of the prayer hall have three balconies each, and the two at the forecourt have two.

Inside, the space under the central dome is open and largely free of furniture, covered with carpets for prayer. Low-hanging chandeliers once held oil lamps, and are now electric. The galleries along three sides were used by worshippers on crowded occasions and are where many of the finest tiles can be seen.

The sultan reached his royal loge through a separate ramped entrance, allowing him to ride up close to the building. This reflected the ceremonial distance between the ruler and his subjects, even in worship.

Funding, criticism and the külliye

Funding and criticism

Contemporary writers recorded unease about the cost. Religious scholars and some contemporary observers questioned whether a sultan who had won no great war should spend so much from public funds. Some critics later linked the mosque’s expense to the financial strains of the period.

Supporters, by contrast, saw it as an act of piety that served the city with schools, a hospital and food for the poor. This debate reflects a wider discussion in Ottoman society about the duties of rulers and the use of state resources.

The külliye

Like other imperial mosques, the Blue Mosque was the centre of a külliye, a complex of charitable and religious buildings. It included a madrasa (college), a primary school, a hospital, a public kitchen, a bath, shops and the tomb of the founder.

Ahmed I died in November 1617, aged about 27, and was buried in the tomb beside the mosque. His sons Osman II and Murad IV were later buried there too. The row of shops below the mosque, the Arasta Bazaar, still functions as a market.

Later history and the mosque today

The Blue Mosque became a central part of Istanbul’s religious and ceremonial life. Sultans attended Friday prayers there in the ceremonial procession known as the selamlık, and the square outside, on the old Hippodrome, hosted public festivities. In June 1826, during the suppression of the Janissary corps, Sultan Mahmud II gathered his loyal troops and supporters at the mosque under the sacred banner of the Prophet.

The mosque is part of the UNESCO World Heritage Site “Historic Areas of Istanbul”, inscribed in 1985. It remains an active mosque, open to visitors outside prayer times. In 2006 Pope Benedict XVI visited it, and Pope Francis did so in 2014. A major restoration, which addressed the domes, minarets and tiles, was completed in 2023.

Timeline

• 1603: Ahmed I becomes Ottoman sultan at the age of thirteen.
• 1606: The Peace of Zsitvatorok ends the war with the Habsburgs.
• 1609: Construction of the mosque begins near the Hippodrome.
• c. 1614: Cafer Efendi writes the Risale-i Mimariyye about the architect.
• 1616: The mosque is essentially completed.
• 1617, November: Ahmed I dies and is buried in the mosque’s tomb.
• 1985: The mosque becomes part of the Historic Areas of Istanbul World Heritage Site.
• 2023: A major restoration is completed.

By the numbers

Legacy

The Blue Mosque marks the end of the classical period of Ottoman architecture shaped by Sinan. Later mosques adopted new styles, including the Ottoman Baroque of the eighteenth century. Architectural historians sometimes find it less inventive than Sinan’s masterpieces, but its sheer scale, harmony and setting have made it the defining image of Istanbul’s skyline.

Facing Hagia Sophia across a garden, it forms one of the world’s most remarkable architectural pairings: a sixth-century Byzantine church and a seventeenth-century Ottoman mosque built on the same principle of a great floating dome.

Why it matters

The Sultan Ahmed Mosque shows how the Ottoman dynasty used architecture to project power and piety, even in a period without great conquests. It is the culmination of a century of Ottoman design and remains a living place of worship and a symbol of Istanbul.