Istanbul is a MUST
It is my second time in Istanbul and it is by far my favourite city. Besides the well known wonders of Sultan Ahmet distric: Aghia Sophia, the Blue Mosque, Grand Bazard, Topkapi Palace.... you can also enjoy a great night life, terrace with amazing views and the nature. Food is so cheap, you can eat for 3 euros, and at a fancy place is almost impossible to pay more than 15 euros. It's a fantastic place for doing some shoppings. Alcohol might seem expensive but cheaper than many other countries.
Insider Tip:I recomend you to take the bosphorus tour that arrives to Yoros casttle, just at the entrance of the Black Sea. Ortaköy is also a must. The pub vivaldi is so good, 2 floors, diferent kinds of music and beer and shoot of Tekila 3 euros!