Mimar Sinan was the chief architect and civil engineer of the Ottoman Empire in the 16th century. Serving as the chief architect during the reigns of Sultan Suleiman the Magnificent, Sultan Selim II, and Sultan Murad III, Sinan created many significant works and gained worldwide recognition both in the past and today. His masterpiece, which he called his "masterpiece," is the Selimiye Mosque in Edirne. In 1538, Sinan became the chief architect of the imperial corps (Hassa başmimarı) and held the position of chief architect for 49 years under Sultan Suleiman, Selim II, and Murad III. Before becoming chief architect, three of his works stand out: the Hüsreviye Complex in Aleppo, the Çoban Mustafa Complex in Gebze, and the Haseki Complex built for Hürrem Sultan in Istanbul. At the Hüsreviye Complex in Aleppo, a single-domed mosque style was combined with side domes at the corners, blending the side-room mosque style followed by Ottoman architects in İznik and Bursa. The complex also includes a courtyard, madrasa, bathhouse, soup kitchen, and guesthouse. The Çoban Mustafa Pasha Complex in Gebze is notable for its colorful stone inlays and decorations. The mosque, tomb, and other elements are harmoniously arranged. Sinan's first work in Istanbul, the Haseki Complex, contains all the architectural elements of its time. The complex, which consists of a mosque, madrasa, elementary school, soup kitchen, hospital, and fountain, has the mosque completely separated from the other parts. After becoming chief architect, Sinan produced three major works that represent the development of his art. The first is the Şehzade Mosque and its complex in Istanbul. Built with a central dome surrounded by four half-domes, the Şehzade Mosque set an example for all subsequent mosques. The Süleymaniye Mosque is Sinan's most magnificent work in Istanbul. According to him, it was constructed during his journeyman period between 1550 and 1557. Sinan’s greatest work, however, is the Selimiye Mosque in Edirne, which he completed at the age of 86 and presented as his "masterpiece" (1575). Throughout his tenure as chief architect, Sinan worked on many different projects. He sometimes restored older structures, dedicating significant effort to Hagia Sophia. In 1573, he repaired Hagia Sophia’s dome, reinforcing it with supportive walls around, ensuring the structure’s preservation to the present day. Part of his duties included demolishing buildings near historic monuments that impaired their appearance. For this reason, he arranged for the demolition of some houses and shops near Zeyrek Mosque and Rumeli Fortress. Sinan also worked on widening Istanbul's streets, constructing houses, and connecting sewers. He raised awareness about fire hazards caused by narrow streets and had a firman (imperial decree) issued on this matter. It is notable that he personally dealt with the pavements of Istanbul, a problem that still exists today. The seal carved on the Büyükçekmece Bridge also reflects his modest personality. In 1976, an impact crater discovered on Mercury was named "Sinan" by the International Astronomical Union in his honor.