The Cistern Basilica was used to supply the necessary water to the city when the city was under siege. 336 columns with Doric and Corinthian capitals, were brought from various locations in Asia Minor for the construction of the cistern. A monumental aqueduct, built by emperor Valens and still a major attraction of the city.

The mosque of Suleyman the Magnificent, located in the center of a large religious complex, stands as the most important work of Architect Sinan, one of the greatest architects in the world history. Built in the 16^th century and stands out as a unique example of classical Ottoman architecture with perfectly integrated sections, beautiful stained-glass windows and the extraordinary harmony of the structural elements.

The Bosphorus is a water pass, that spans 36 km. between the Black Sea and the Sea of Marmara. On either side of the strait, stands the two medieval castles built by the Ottoman Turks for the conquest of the city; the small but pretty Anadoluhisari (14^th cen) in Asia, and right across, the awesome Rumelihisari, constructed in the 15^th cen. Dolmabahce Palace, that reflects the splendor of the late Ottoman architecture, is a monument of wealth, decorated with beautiful Hereke carpets, chandeliers, of European crystal and a rich collection of paintings. A must see.