Istanbul is an old city that was popular even back in the times of the empires. The popularity of the city is one of the reasons it is the most crowded city in Turkey and the fact that it is the most developed metropolis in the country. Housing more than 15 million people, Istanbul is a center for both tourists and business settlements. The popularity of the city and the range of possibilities it offers have resulted in the establishment of many universities in Istanbul. Currently, the city has 57 universities that are either public or private universities. Public universities in Istanbul have a more rooted history than the private ones thanks to the works of the Ottoman emperors who valued education and the earlier times of the Republic of Turkey. Istanbul University, for example, dates back to the medieval age as it was established by Sultan Mehmed the Conqueror right after the seizure of Constantinople. Istanbul University offers a variety of subjects for higher education, and it is a university of recognition in international areas.