The Ahmet III fountain, built in 1729, stands at the entrance to Topkapi Palace. Deep overhanging eaves shade the water spouts where the parched could stop for a cup of refreshing water. Mahmut II built the Beyazit Tower (85 meters high) in 1828 as a fire tower. Today it stands within the grounds of Istanbul University.
The Bozdogan-Valens aqueduct, built in 368 AD ,supplied the Byzantine and later the Ottoman palaces with water. Today, pan of the remaining 900 meters of double tiered arches straddle the major highway that runs through the old part of town.
The Istanbul land walls, once an impenetrable fortification, stretch seven kilometers from the Sea of Marmara to the Golden Horn.
Restored recently, and many times previously, these walls date to the fifth century and the reign of Emperor Theodosius II. UNESCO has declared the land walls, and the area which they enclosed, one of the cultural heritages of the world.
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The Galata Tower, a Genoese construction of 1348 rises 62 meters high across the Golden Horn. From the top you see a marvelous panorama of the Golden Horn and the Bosphorus.
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Rumeli Hisari, or the European Fortress, was built by Mehmet the Conqueror in 1452 prior to his capture of Istanbul. Completed in only four months, it is one of the most beautiful works of military architecture in the world. Used today as an open air theater, it is also a favorite weekend picnicking location. (Open every day except Mondays.)
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Leander's Tower, Kiz Kulesi first constructed in the 12th century on a tiny island at the entrance to the harbor. The present building dates from the 18th century.