Starting from the tip of the Historic Peninsula the tour passes, in (approx. 1hr 30 min.) in front of the leading Ottoman palaces like Topkapı,Dolmabahce and Beylerbeyi, and the shores of the Bosphorus lined with traditional wooden built villas on its shores and other monuments and places of interest. RumeliCastle comes next. Situated on the European side of the Bosphorus, it was built by Sultan Mehmet the Conqueror in1452 to control sea traffic from the north and prevent it from entering Constantinople. The Bosphorus is approximately 30 km long, and at its narrowest point, Anadolu and Rumelicastles face each other. Here the width of the strait is about 800 meters. The waters of the Bosphorus flowfrom the north to the south towards the Sea of Marmara on the top and there is current in the opposite direction on the bottom that flows upwards. This current is very powerful in places and reaches a speed of approximately 6 knots around Arnavutköy. The currents also change direction at various times during the day. These currents have always constituted a threat for the sea traffic crossing the strait. The Bosphorus straits have an average depth of 50 meters and a maximum depth of 110 meters. Because of the currents and the different temperatures on various layers of the water making the Bosphorus a paradise for fish. The fish migrate between the Black Sea and the Marmara according to the season. These fish, specific to these waters, are caught during the migration seasons and they are famed for their taste. Up to the 1800’s, the settlements along the Bosphorus were sparse due to the strong currents and the lack of roads. They consisted of a few villages, some imperial palaces and the mansions of the wealthy. In the 19th century the embassies started to build their summer residences on its shores. Today the shores and the hills are rapidly being transformed into residential districts. There are also numerous fish restaurants and cafes on both sides of the shores of the Bosphorus. Modern villas intermingle with the some of the last remnants of old wood based seaside mansions that have been preserved. One of the most beautiful sights in the world, the Bosphorus is a strait winding between two continents and joining two seas. The Black Sea is connected to the Sea of Marmara through the Bosphorus and the Dardanellesstraights at the southern mouth of Marmara connects with the Aegean sea. The tour offers magnificent vistas and a good historical background to the city.