Topkapi Palace: As the administrative center, for nearly 400 years, for the Ottoman Empire, which was one of the greatest empires of the world, Topkapi Palace is certainly the most important historical site to be visited in Istanbul. In 1461, less than ten years after the Conquest, Fatih Mehmet ordered the construction of Topkapi Sarayi a palace that would be known as Dar-üs Saadet, the "House of Felicity". Topkapi Sarayi remained the seat of the Ottoman Sultans until 1868, when Abdülmecit I moved to the European-style Dolmabahce Palace farther up the Bosphorus.
Süleymaniye Mosque: Suleymaniye is without question one of the greatest works of its architect, Sinan. Begun in 1550, the mosque was completed in 1557, with two more years required in order to finish the entire complex.