There is so much to see in Istanbul, it can be overwhelming. We were meeting my parents (Charles and Bev) there and knew we wanted to see the major sites as efficiently as possible to have time to just relax with them.
Upon recommendation, we booked a day-tour of Old Town through Neon Tours and requested the highly recommended guide, Gulay. This was a great decision. Gulay took us through the Old Town hitting all of the major sites including Hagia Sofia, Blue Mosque, Basilica Cistern, Grand Bazaar & Spice Market. She was a wealth of historical knowledge and even laid out our next day of site seeing across the river.
Having knocked out the major sites, we spent the next few days actually trying to see less. While Istanbul is known for the food, we left a bit disappointed. Even in the nicer restaurants it seemed the menu was just a "fancier" version of traditional Turkish cuisine. It wasn't bad, but it was a bit bland.
Our top recommendations for Istanbul are below:
Suleymanye Mosque: Located up a hill just outside the Grand Bazaar, this was our favorite mosque. It's giant, but much less traveled by tourists, and the inside is beautiful. It also offers the best views of the city. It's worth the hike up to the top.
Basilica Cistern: The main water storage for the city during Roman times offers an incredible glimpse into just how modern the Roman Empire was. This small portion that you see is only 10% of the actual cistern. It blew our mind a bit. It's also a nice break from the heat.
Dolmabache Palace: With a prime real estate location on the Bosphorous River, the palace is overwhelming in its opulence. You are required to go with the tour to see the palace and it moves quickly, but don't bother trying to pay attention to the guide, yelling over the other tour groups both in front and behind you. Just wander along and look around. Tip: Don't waste your time on the harem here. Do the one at Topkapi Palace instead.
Bosphorous Cruise: Just under the street from the New Mosque is a company called Tuyol offering an hour and half cruise for 15 lira/person. This is the best and quickest way to see the shores. A longer cruise would probably be a waste of time; our cruise was sufficient to see everything on the river. If facing the New Mosque, sit on the left side for the best views along the cruise.
Unfortunately, we don't have any overwhelming MUSTS for food in Istanbul. Most of our experiences, even those recommended by several people, turned out to be just average.
My one recommendation for food though would be to try manti - a mini ravioli stuffed with meat and garlic yogurt sauce. So delicious. Kebaps are ubiquitous, so try many styles and vendors, and decide on your own favorite.
We got to experience the breaking of the fasts during Ramadan and witness families coming together in the parks to share a meal at sundown. This was so special to see. There was also a beautiful craft market beside the Blue Mosque area which was reminiscent of the Altenmarkets of Germanic Christmas. Fast-breakers would stroll among the shops after finishing their family meal.
We really did love Istanbul. Sharing the experience of the city with my parents was the perfect cap to our 3 weeks exploring western Turkey.