Mimar Sinan was the greatest Ottoman architect, serving as the chief architect from 1539 until his death in 1588. During his long career under three Sultans, he built over 300 buildings, including mosques, palaces, hospitals and schools. His innovative designs helped establish classical Ottoman architecture, with his masterpieces including the Suleiman Mosque in Istanbul and the Sultan Ahmed Mosque. As no successors matched his skills, Ottoman architecture began to decline after his death.