One my favorite activities in Istanbul is taking the car ferry between Harem (a district on the Asian Side of Istanbul) and Sirkeci. If I was to come here for just a couple of days and I didn’t have any time to get in the sights, taking the ferry would make up for it. It is basically a commuter ferry so you get to mingle with people from all walks of life. Although no one ever bothers with checking the time of the ferry (they just show up and wait for the ferry to return from the other side) This link shows the current schedule. You can tell it’s for the locals only since the page is only in Turkish. But for those who want to research where/when/how/how much, you can research “Sirkeci-Harem Arabali Vapur”. This is the kind of adventure one should just jump into. Get to Sirkeci- the ferry terminal is right across from the metro stop aligned with the main train station. Sirkeci is full of ferry stations but this is the only one for cars and it is operated by IDO (Istanbul Deniz Otobusler) Hop on and you go on one of the most scenic cruises right across the Bosphorus. You can even do roundtrip – it costs the same as riding any other public transportation for pedestrians.
You must drink a glass of Turkish tea, sit back and enjoy the view.