The lighthouse that set the bar for all future lighthouses, the monumental Lighthouse of Alexandria, commissioned by Ptolemy I and built in 300 – 280 BCE by Sostratus of Cnidus, is believed to be the first lighthouse in the world. The spectacular 330ft tall building was for centuries the third tallest building in the world after the pyramids of Giza. A burning fire on top of the structure of three levels: a square level at the bottom, an octagonal level in the middle and a cylindrical top, guided men at sea until the lighthouse was gradually demolished by earthquakes between the 12th century and late 15th century and transformed into a medieval fortress by Mamlūk sultan Qāʾit Bāy.