Historians trace back the history of Istanbul University to the 15th century. Three educational institutions are associated with the history of Istanbul University. The first is the medrese founded by the Otoman Sultan Mehmed II in Istanbul following the conquest of the city; the second is the Darülfunun, where education was regularly given from 1900 on; and the third is the Istanbul University established in 1933 by the University Reformation initiated by Atatürk. The present article gives a short history of these three institutions, dwelling on the history of its central building, the university gardens, the library of rare collections, and the history of the buildings housing the Faculty of Pharmacy, The Faculty of Science, the Faculty of Letters, the Biology Department and the Department of Astronomy.