The Bosporus or Bosphorus, also known as the Istanbul Strait, is a strait that forms the boundary between the European part, Rumelia, of Turkey and its Asian part, Anatolia. The world's narrowest strait used for international navigation, it connects the Black Sea with the Sea of Marmara (which is connected by the Dardanelles to the Aegean Sea, and thereby to the Mediterranean Sea). It is approximately 30 km long, with a maximum width of 3,700 metres at the northern entrance, and a minimum width of 700 metres between Kandilli and Aşiyan; and 750 metres between Anadoluhisarı and Rumelihisarı.
The cheapest way to experience Bosphorus in Istanbul would be to take one of the public ferries that travel between the Anatolian and Rumelian sides of the city. They depart every 45 minutes, and cost about $1. There are also faster ferries that take off every 10 minutes, but the slower ones will give you more opportunity to see the city. You can also take a ride on a variety of tourist ships, from modern ones to Ottoman style ones.
We took the Bosphorus Ferry on a sunny sunday from Eminonu to Anadolu Kavagi for a full Bosphorus cruise.