Bosphorus Cruise
The best way to see the bosphorus in all its beauty is to take a boat trip. this is the strategic waterway connecting the black sea to the mediterranean, and dividing istanbul into two continents. as the boat zigzags between asia and europe, you can admire the old ottoman wooden houses, 6 ottoman palaces, 2 suspended bridges, and 2 medieval castles.
It is somewhat of a tourist trap. Oneway is 13 lira, retour 26. The standard price for one hop for locals is 1.5 lira. On sundays there are fewer boats.If you are not so lucky/fast to get one of the few deckseats it gets very hot inside, even hotter than in the city.
There are also daily trips from Eminönü, by 10.30AM in the morning and come back by 4.30PM in the evening. It costs 20 YTL per trip per person. There is an additional boat by 1.30PM in summer.
For travelers that don't want to bother with getting off the boat/taking the bus to take a deeper look into some of the Bosphorus neighbourhoods, there are also boats departing from Ortaköy which allow you to see waterfront from a distance up to the Second Bosphorus Bridge in the north, though they don't allow you to get off at any neighbourhood quay you like in fact they don't stop anywhere until they get back to Ortaköy.