2-day Istanbul Tour
Day 1 Full day Istanbul. Overnight in Istanbul.
Obelisk  Hippodrome
Blue Mosque (Sultanahmet)
St Sophia (Ayasofya)
Sahaflar Carsisi (Old book bazaar) 
Grand Bazaar (Karpali Carsi) walk downhill thru local markets to Spice (Egyptian) market. 
Boat trip on Bosphorus 
Day 2 Full day Istanbul. Overnight in Istanbul.
Topkapi Palace 
Walking tour  
-- Rustem Pasa Mosque 
-- Galata Bridge
-- Tunel funicular to Galata Tower 
-- Taksim Square / Flower market (Cicis bazaar)
Note: Tours may vary slightly depending on local conditions and group interests