Take the Tram to the Tophane stop. Wander the streets of Cukurcuma which is a great neighborhood for antiques buffs. Walk the hilly backstreets in this area of Beyoglu. Check out A La Turca at Faikpasa 4 in a four floor townhouse.
Walk to Cihangir and find a café for lunch. Walk to Taksim Hill and Taksim square and then stoll down the pedestrian Istiklal Caddesi. If you have time, check out the Pera Museum or the Istanbul Museum of Modern Art.
The Pera Palace Hotel has just reopened after an extensive renovation. You might check it out for tea. The hotel was one of the first luxury hotels where Orient Express train passengers overnighted.
Have a drink or dinner at 360 Istanbul. This is a glass penthouse restaurant on top of a 19th century apartment building. Great views of the city. Istiklal Caddesi 32/309, phone 0212 251 1042.
I liked the fact that there was some great contemporary architecture and design in Istanbul in contrast to the very traditional architecture of the historic palaces and mosques.
I really loved my time in Istanbul. I loved the old world charm, colors, mosques, and the warm friendly people. Make sure this is added to your list of places you need to visit!