Everything is cheap, people are really friendly and are offering to help (without wanting money afterwards, like in Bulgaria) and there is a lot to see (such as the great mosques, the Turkish dervishes and the catacombs), try (haggling at the spice & silk market, ride the hot air balloon and go up the Galata tower) and taste (Turkish delight, Turkish coffee and real kebab).
When I first came to Istanbul, I was surprised how overwhelming the city was. With a population of 12 million people and all the tourists who where there during the high season it felt like it was a New York of Eastern Europe. I don´t want too sound too cliché, but I must admit that I have fallen a bit in love with Turkey.
The first day I spent walking around looking at the touristy things on the European side, when I heard someone call my name. I then turned around to see a friend who I was studying with a few years ago in Norway and her boyfriend. We were both surprised to see each other in the second biggest city in Europe, and decided to have some beers by the view of the hostel rooftop and go to a couchsurfing party afterwards. There I also met people I had gotten to know in a hostel in Serbia, and I also found someone who was willing to host me the last nights in Istanbul. This guy lived on the Asian side of Istanbul, which was perfect as I then got to take the ferry over, and have someone guiding me through the part of Istanbul which I had not yet seen.
I feel like four days was not enough for such a huge city, and wish that I could use my whole three month Turkish visa to stay here in Istanbul.