Once in the square for the Hagia Sophia ( expect queues so book online) the Blue Mosque is close and the basilica system, as is the oldest and most traditional place to eat Kofta Just ask. Long queue but quickly moves as quick turnover Go to the Topkapi palace and a must- the Grand Bazzar and haggle Hope this helps

I would recommend you to get a guide once w/ the guides you can skip the lines. The highlights are Hagia Sophia, Topkapi Palace, the Cisterns and the Hippodrome ( Those four are all at the same area, as the Blue Mosque) After it you can walk to the Grand Bazar. On the way, you can stop to eat in the Antakya restaurant. After walking the Grand Bazar go to see the Suleiman Mosque, it's fully restored and "less fashionable" than the Blue Mosque (that it's crowdy and you can't see nothing because of the restoration works). Start early in the morning (in Turkey it means 9:00) you will be able to do all this in one day. The place you will spend more time visiting is the Topkapi Palace. If you have time, you can get a cruise in the Bosphorus, but with one day I don't believe you will be able to do it. The places you will miss are Dolmabahce Palace, Cora Church, and the Constantinople walls. At night go see the Golden Horn and Galata Tower, and go eat a Baklava in the Karakoy Gulluoglu Mumhane Cad. No:171 Karakoy it's "near" to Galata tower and they say it's the best Baklava from Istambul.