Restoration work at Istanbul’s Süleymaniye Mosque, a landmark of Ottoman design, has uncovered hidden acoustic vessels inside its dome, 16th-century decorative paintings and calligraphy preserved on a metal surface, shedding new light on the engineering techniques of architect Mimar Sinan.
Commissioned by Ottoman Sultan Suleiman the Magnificent and completed on Oct. 15, 1557, the mosque is regarded as Sinan’s “masterpiece of the journeyman period.” The wider Süleymaniye complex includes religious schools, a hospital, a public kitchen and a bathhouse, reflecting the Ottoman approach to urban planning and social welfare.
Kaya Üçer, an associate professor at Mimar Sinan Fine Arts University who participated in the restoration, said the work had helped distinguish architectural evidence from long-standing popular beliefs about the building. One discovery concerned the mosque’s renowned acoustics. During restoration, workers erected approximately 20,000 cubic meters of scaffolding, allowing specialists to examine parts of the dome inaccessible from the floor.
“By chance, during repairs to some cracks in the dome, we found pitchers at the bottom, used alongside bricks,” Üçer said. “When you look up at the dome from below, you cannot see them. But from above, you understand that the openings soften the sound coming from below and prevent echoes.” The vessels, installed vertically in a zigzag pattern with openings at their bases, were examined through acoustic tests.
The dome also contains elaborate Baroque and Rococo-style floral decorations, despite the building’s origins in the 16th century. Researchers examined its painted layers under ultraviolet light and through careful scraping to identify earlier designs. They found traces of another decorative scheme beneath the existing ornamentation, suggesting that different designs had been tested before one was selected. The restoration team preserved the surviving historic elements while repairing the visible decorations.
Another unusual feature was found in the structure supporting the dome’s calligraphic inscription. Although the writing is traditionally associated with calligrapher Ahmed Karahisari, historical records also name his student Hasan Çelebi, while later restoration work is said to have included corrections by Abdülfettah Efendi in the 18th century. Üçer said the inscription’s background included a zinc surface, fastened with large nails, beneath a gold-leaf-covered wooden frame. The writing on the metal surface appeared to have been designed for exceptional durability. The team also identified a missing letter in the inscription and, after consulting calligraphy specialists, restored it in accordance with the scientific committee’s assessment.
Elsewhere, scraping work in the mosque’s arcades and the imperial gallery revealed original decorative paintings from Sinan’s era, including rumi motifs widely used in 16th-century Ottoman art. Missing sections were reconstructed based on surviving examples. The team also located a broken piece of the fountain’s water-level measuring structure in a museum in Istanbul’s Fatih district and confirmed that it fitted the missing section.
Üçer said the restoration had taken a period comparable to the mosque’s roughly seven-year construction and had been designed to protect the historic structure from requiring another major intervention for approximately 50 years.
