Secondary Use of Ornamental Features. Ottoman architects and builders like the Ayyubids and Mamluks before them, made secondary use of various ornamental elements from buildings constructed mostly by the Crusaders, who had ruled Jerusalem in the 12th century. Only very few of the some thirty churches and structures built by the Crusaders are still standing. Some churches were converted into mosques, others were destroyed. The use of pre-Ottoman decorative elements is particularly evident in the magnificent public water fountains, known as sabils, built in the Old City and environs during Sultan Suleiman’s reign in the 16th century.